Tell me about it. Hard coded fills have always been a cause of frustration. And now GS is changing the fills that we can and can't delete, without any documentation!
I wish we were simply allowed to create empty & solid fills as we do any other fill, and get rid of hard coded fills altogether. How hard could it be?
From a purists point of view, there is an inherent problem with deleting fills that are set up as defaults within library parts or tools. (Or any attribute for that matter.) At my last count there were about 24 fills that would come back to haunt you if you deleted them. And don't start me on materials! A consciencous CAD Manager cannot simply delete every attribute (allowable) and not risk having MISSING attributes appear constantly as they are accessed. Parts in the Extras menus are especially troublesome when it comes to fills, and just about every 3D part accesses an ArchiCAD material.
One solution would be if GS listed any missing attribute's name. Eg. MISSING (Common Brick), instead of just MISSING. Then at least we could use Attribute Manager to bring them back in.
Maybe somewhere in the future, attributes will optionally be brought in with each part, as they are with merged files, which will give us much more control over what is brought into our clean templates.
It would also be nice if Attribute Manager correctly & concisely indicated whether and where a used attribute (ie. indicated by a tick) was actually being used, but I don't want to flog that dead horse again!
Cheers,
Link.