To create rectangular buildings I use the "Drawing" toolbar which also allows to create L-/H-shaped buildings etc. However I can only define the colours of outline/area and not assign any attributes like 'age of house', 'social status of owner' etc.
When I create a polygon feature I can assign all the attributes that I need, but there is no option for creating 90° angles when digitizing. Any ideas?
When you use the drawing toolbar you are simply creating a temporary drawing that is not a saved layer outside the program and does not have a table attached to it. This means you cannot attach attributes to it. You need to create a feature class to be able and then create the field you require within that feature class. I can't direct you on how to do this unless you tell me which program you are using to attempt this.
as for the 90 degree angles there is a way in arcpro and I'm sure desktop as well but once again I need to know which program you are using before I can advise any further.