How to make User Presets Sticky and Locally Shared  

As far as 1) is concerned, sure you can. I have created a directory on OneDrive with the PrusaSlicer settings, and I use symlinks on Windows PCs and Macs to redirect the standard settings folder to that shared directory. Alternatively you could launch Prusaslicer with the -datadir flag to point it to the shared directory. 

As far as 2) is concerned, I don't know. I haven't lost my settings during an upgrade. If that happens to you for some reason, I would probably try to copy the setting directory before the upgrade and then simply put all files back after the upgrade

Export a config bundle

Use File->Export to create a config bundle. That will create a text file that contains all your custom presets. You can then sync this over to the other computers and import it into PrusaSlicer there. 

I've got some notes on the procedure here that might be helpful.

Any custom presets you save that are based on the standard prusa ones have the potential to be affected when prusa update the base profiles that they are based upon.  At least while the dependencies are intact.
If you want to make sure that they aren't subject to that then remove the dependency link and save the preset afterwards.  That way it doesn't not matter what changes prusa make.

Also the export Config bundle suggested by Bob is an eminently sensible back up solution that should be done regularly anyway just on general principles.  The bundle can be stored offline and is always there if required just like any other backup.

Ah dependencies...

Heh. Good point. Notes on detaching sysetm profiles here.

inheritance and overlays

Thanks for all the suggestions and tips.  I particularly found Bob's Project Notebook interesting and full of lots of useful information.  I was pretty interested in the inheritance and dependencies but it raised another question with me.  I only have a couple print profiles I modify significantly however I make the same three changes to almost all of them.  Rather than create my own custom profiles for every system print profile I use, is there a way to have it automatically load an overlay after loading a system preset? Or tell it somehow to inherit the previously loaded settings in a custom profile?

Something like this (doesn't work - just illustrating what I am trying to do):

inherits = *previous*
perimeters = 3
fill_pattern = triangles
output_filename_format = {input_filename_base}_{filament_type[0]}_{printer_model}.gcode

@ticktock

You can, if you dare, edit "PrusaResearch.ini".
In prusaslicer, "Help" -> "Show configuration folder", goto "Vendor" folder
Copy "PrusaResearch.ini" to "PrusaResearch.BAK", just in case.
Edit "PrusaResearch.ini" to suit your needs
Save file.
Prusaslicer does not have a single file for each of the built in presets, PS takes them from "PrusaResearch.ini" when PS start

Keep track of your changes, they will be overwritten if/when Prusa make an update..

Yes, I have done it, took away the skirt, change order in output filename, decrease elephant foot.

@ticktock

And one more important thing.
Prusaresearch.ini will not be included if/when you export config bundle!

Inheritance is the answer, but it has serious limitations

Posted by: @ticktock

[...]  Rather than create my own custom profiles for every system print profile I use, is there a way to have it automatically load an overlay after loading a system preset? Or tell it somehow to inherit the previously loaded settings in a custom profile?

You've got the right idea, but you're running into limitations on the way PrusaSlicer currently works. You can create a config bundle file containing multiple presets of each type (print, filament, and printer). Presets can inherit from previously defined presets. Unfortunately, there are limitations:

• A preset can only inherit from a preset in the same config bundle (.ini) file.
• Inheritance is only applied when the config bundle is first imported. After that, the sub-presets are fully expanded and changes to the "parent" will have no effect on the "children".

Unfortunately, the only solution is to maintain your own master config bundle file. I've done this here for example. I've got more notes on this topic here that might be of interest.

So that's where it is...

Posted by: @ringarn67

@ticktock

You can, if you dare, edit "PrusaResearch.ini".
In prusaslicer, "Help" -> "Show configuration folder", goto "Vendor" folder
Copy "PrusaResearch.ini" to "PrusaResearch.BAK", just in case.
Edit "PrusaResearch.ini" to suit your needs
Save file.
Prusaslicer does not have a single file for each of the built in presets, PS takes them from "PrusaResearch.ini" when PS start

Keep track of your changes, they will be overwritten if/when Prusa make an update..

Yes, I have done it, took away the skirt, change order in output filename, decrease elephant foot.

I had tried this before but failed because I was editing the PrusaResearch.ini in the installation directory.  You instructions on where to find the relevant file was what I needed.  Thanks!