I want to edit the wall width in the Wall Properties, but it's not editable. Or - how do I change default width from 4-1/2 to 5-1/2? Thanks.
Assuming you're using smart walls, you need to use the Wall Type Manager instead. Open the WTM and then in the Line Properties menu, pick Line and change it from 1 to 2 (assume the wall is a simple two line wall). The Offset from previous line will then display the current wall thickness. Enter a new thickness and then pick Save at the bottom of the menu.
Note - if you want to retain the existing wall type and its thickness (ie. not change any existing walls in your drawing), pick Save As instead and enter another wall type name which is different to the current one. Doing this will then give you 2 wall types, one at the current thickness and the new one you are now creating. Any existing walls in the drawing at the current wall thickness will remain unchanged.