Hmmm......
Call me mad :lol: but I've just checked this out on one my my main systems, an A4000 with Picasso-II, scandoubler and running OS3.9.
I put copies of the 'PicassoII' icon from Devs/Monitors, 'ChangeScreen' from WBStartup and the 'screenmode.prefs' file from Workbench:Prefs/Env-Archive/Sys onto a blank floppy disk, and then deleted them all :-o
The A4000 then booted into a rather colourless HiRes Workbench screen and I was able to go into Prefs/ScreenMode and see Save Use and Cancel without problem.
As it was to hand from yesterday, I then also booted into a Workbench 2.05 floppy. There was no problem to swap disks and put the files 'PicassoII' and 'ChangeScreen' back in from here. Oddly enough, after a reboot the A4000 was in 640X480 16Bit without a 'screenmode.prefs' file being present, so there must be a reference to it in another file. But I clicked Save anyway and a new 'screenmode.prefs' file miraculously appeared in Workbench:Prefs/Env-Archive/sys :-)
@ ral-clan
I have indeed come across your problem of not being able to see Save Use and Cancel, but I can't remember under what circumstances.
A4000 Mad