13 has an 'Embedded Library' where as 12 doesn't.
If the doors and windows were in the embedded library then this is possibly why they are missing.
I think when converting from 13 to 12 you should have been prompted to save the embedded library objects to a separate folder.
Problem is these still may be version 13 format so can't be read in 12.
I can't be sure as I don't have 13 installed.
If they weren't in the embedded library (but in the default 13 Archicad libray) then you could try deleting the version 13 library and loading the version 12 library.
I am not sure if doors and windows were the same in both version (i.e. had the same GUID numbers) as i don't use the default libraries and I don't have 13 installed.
You can't save objects back to older versions but you can create a new object in 12 and copy and paste all the scripts across from 13.
You would then need to manually create each parameter in the parameter list which could be a lot of work.
But then you will have a new GUID number so the object wouldn't recognised automatically.
You would probably have to select the missing window and then replace it wth the newly created one.
It may be easier to just delete and replace the windows with ones that you have.
Barry.
One of the forum moderators.
Versions 6.5 to 27
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11
