RE: Can you use a half damaged smooth sheet?
you can use the backside of your sheet, or you can place your models in prusaslicer around the damaged spot.
RE: Can you use a half damaged smooth sheet?
Yes, I had a smooth sheet that had one damaged side which I used for the better part of two years before the second side got hosed and I re-skinned it.
I used the damaged side for smaller parts.
In the photo below, the coating has been torn off to the top and left of the print.
RE: Can you use a half damaged smooth sheet?
Yes you can. You can also continue to use that side so long as you plate your prints to avoid that spot.
While I've never tried it you may be able to resurface it with a PEI sheet.
https://www.prusa3d.com/product/pei-ultem-sheet/
This shows how to do it on the mk2/3 series
https://help.prusa3d.com/en/guide/replacing-the-pei-sheet-on-the-mk3s-mk3-mk2-5s-mk2-5_23920
You'd need to trim it for the mini and it should be a little easier with the steel sheet as you don't need to unfasten it from the printer.
Cheers
-Bob
Prusa I3 Mk2 kit upgraded to Mk2.5s, Ender3 with many mods, Prusa Mini kit with Bondtech heat break, Prusa I3 Mk3s+ kit