Open the library part directly (command opt "O") change the parameters and save with a new name (if you change the A,b or zzyzx settings it will effect all the previously placed library parts). So a new object is in order.
That said the other parameters can be changed without effecting the placed library parts (same for windows and doors)
Cheers John
John Hyland : ARINA : www.arina.biz
User ver 4 to 12 - Jumped to v22 - so many options and settings!!!
OSX 10.15.6 [Catalina] : Archicad 22 : 15" MacBook Pro 2019 [/size]