This is what I use, I keep the link to Joan's first post in this thread about this because I'm using her comment (and so I can find this thread again). I hadn't really realized how much I've added to it since first seeing her post...

{if layer_z=4.74}; Pause to insert objects
M400 ; wait for movement buffer to empty
M300 ; beep
M104 S0; Turn off extruder heater to avoid too much oozing
; code snippet originally Prusa forums joantabb here: https://forum.prusa3d.com/forum/original-prusa-i3-mk2-s-others-archive/pause-print-in-gcode/#post-125758
G1 X10.000 Y200.000 E0; parking position GET THE PRUSA TO STICK IT'S TONGUE OUT! (edited to revise Y coordinate)
M400; wait for bed to stop moving
M300; beep again
M84; disable motors (may not be necessary)
M0; user stop
G28 X Y; Home X and Y (only) to correct for accidentally moved bed or extruder (it is assumed Z didn't move because that is a harder axis to manually move).
M109 S; return nozzle to printing temperature
{endif}

Change the layer_z value to what is required for your print, copy the full if...endif statement as many times as you need to pause and enter the proper layer_z value for each copy.

An error above earlier in this thread is using M105 to turn the hot end heater back on. (May originally have been a typeo that never got caught.) M105 only returns the temperatures to the console and M0 doesn't seem to turn off either the hot end nor the bed heaters. Turning off the hot end reduces oozing while paused but the bed stays hot so the part doesn't pop off of a cooling bed.

I haven't had any problem with the re-homing causing any layer shifts... Maybe I'm lucky? I like the idea above about moving the z axis up, but I wasn't sure if this would be executed before or after the generated gcode to move to the correct z height. If I put a z axis up command in, I'll use what I modified the original end gcode Z-height lift to after I decided 3cm above a low print doesn't get the z height high enough to clean the nozzle after a low print:

{if layer_z < max_print_height}G1 Z{z_offset+min((layer_z/max_print_height)*(max_print_height-100)+100, max_print_height)}{endif} ; Move print head up proportionally of print height to max 

This formula basically moves the Z to a height in the upper 10cm of the print volume proportionate to where the current z height is to the full print volume. I'm not sure how the z_offset works into this formula, but it was in the original code from Prusa. I figured if I didn't know what it was for I would leave well enough alone.

@sembazuru If i am not mistaken to add a pause now with the new custom g-code insert I don't need to add the {if layer_z=x.xx}...{End if } and just paste the rest of your code ?  

Ho wait... the Pause option is there to I completely forgot I used the custom g-code to configure a temp tower and have not register there a pause option in there now 😆  But its only a pause no move  So  your code is still better.  Have you experience with the M17 instead of homing? 

Here what pause seems to add:

;AFTER_LAYER_CHANGE
;94.8
M117 Place the "bolt" in slots and resume printing
M601

I have been referring to this thread many time so thanks for all that guide us to be better maker!!! 👍 🍻 🥂 

I'd like to use some of the ideas you've compiled here to achieve something you should (imo) be able to do in PrusaSlic3r with the ColorPrint feature (but currently can't): change filament mid-print to a different kind of filament. The ColorPrint solution (which uses M600) won't allow you to change parameters such as extruder temperature between ejecting the old filament and loading the new. Personally I need this because I'd like to experiment with adding one or two layers of something like FLEX on top of an object printed with ABS or PLA in order to get a less slippery surface.

From what I gather, this might be the best way to do it:

M400 ; wait for movement buffer to empty
G1 Znnn ; move up a bit
G1 X10.000 Y200.000 E0 ; move aside
M400 ; wait for movement buffer to empty
M702 ; unload filament
M109 Snnn ; set extruder temperature for new filament and wait until reached
M300 ; beep
M1 Press any key to continue... ; wait for user to press button
M701 ; load new filament
G28 X Y ; re-home X and Y axes, just to be sure
G1 Xnnn Ynnn E0 ; return back to where we were on the XY plane
G1 Znnn ; restore Z

The idea is to slice the model two times with (mostly) the same settings except the filament preset and to use the ColorPrint feature to have the M600 code inserted in both files at the same layer; then split the files by the M600 lines and re-join the appropriate parts with this piece of Gcode in-between (obviously filling in the nnn's using values from the appropriate file). Does that make sense? :-D Or is there another approach you'd recommend?

Fantastic code!  Thanks for taking the time to post this.  I kinda see what you are saying with the Z axis.  Thanks.

{if layer_z=4.74}; Pause to insert objects
M400 ; wait for movement buffer to empty
M300 ; beep
M104 S0; Turn off extruder heater to avoid too much oozing
; code snippet originally Prusa forums joantabb here: https://forum.prusa3d.com/forum/original-prusa-i3-mk2-s-others-archive/pause-print-in-gcode/#post-125758
G1 X10.000 Y200.000 E0; parking position GET THE PRUSA TO STICK IT'S TONGUE OUT! (edited to revise Y coordinate)
M400; wait for bed to stop moving
M300; beep again
M84; disable motors (may not be necessary)
M0; user stop
G28 X Y; Home X and Y (only) to correct for accidentally moved bed or extruder (it is assumed Z didn't move because that is a harder axis to manually move).
M109 S; return nozzle to printing temperature
{endif}

Change the layer_z value to what is required for your print, copy the full if...endif statement as many times as you need to pause and enter the proper layer_z value for each copy.

An error above earlier in this thread is using M105 to turn the hot end heater back on. (May originally have been a typeo that never got caught.) M105 only returns the temperatures to the console and M0 doesn't seem to turn off either the hot end nor the bed heaters. Turning off the hot end reduces oozing while paused but the bed stays hot so the part doesn't pop off of a cooling bed.

I haven't had any problem with the re-homing causing any layer shifts... Maybe I'm lucky? I like the idea above about moving the z axis up, but I wasn't sure if this would be executed before or after the generated gcode to move to the correct z height. If I put a z axis up command in, I'll use what I modified the original end gcode Z-height lift to after I decided 3cm above a low print doesn't get the z height high enough to clean the nozzle after a low print:

{if layer_z < max_print_height}G1 Z{z_offset+min((layer_z/max_print_height)*(max_print_height-100)+100, max_print_height)}{endif} ; Move print head up proportionally of print height to max 

This formula basically moves the Z to a height in the upper 10cm of the print volume proportionate to where the current z height is to the full print volume. I'm not sure how the z_offset works into this formula, but it was in the original code from Prusa. I figured if I didn't know what it was for I would leave well enough alone.

G1 X10.000 Y200.000 Z100.000 E0; parking position GET THE PRUSA TO STICK IT'S TONGUE OUT! (edited to revise Y coordinate)

I added a Z100 so that I can clean the PETG goop off the nozzle.  

The absolute Z100 will come back to haunt you; any Z move should take into account current Z position (aka - current print height).

;Pause Print Here 
G1 X10.000 Y200.000 Z100.000 E0; parking position GET THE PRUSA TO STICK IT'S TONGUE OUT! (edited to revise Y coordinate)
M1; user stop
M105; return to current temp
;Resume Print Here (with Octoprint resume)

I added a Z100 so that I can clean the PETG goop off the nozzle.  

What exactly is the bug in the M601/M602 process proposed earlier? I would prefer to have the nozzle cool down during the pause, so as not to cook the filament if I'm not there to respond immediately (overnight prints!).

Yes, I could obviously insert the temp codes manually into the gcode file, but it's another step and a possible source of mistakes (just lazily copy+pasting from a previous print could, for example, result in a PETG print resuming at PLA temperature). Having the printer store the "temperature of the day" is safer.

/Torsten

Use the placeholders ... they include the filament profile temps...

M109 S ; set & wait 1st layer extruder temp

or 

M109 S ; set & wait other layer extruder temp