Using the latest Windows Store version (which says v7.6.2 in the About... dialog), I was unable to modify wall thickness - or, generally, do anything in the Modify Walls... dialog box. When clicking Ok here I got a popup prompting to sign up for a paid version - there was no apparent way to click Ok in the dialog without paying.
I was able to (somewhat) work around this in v7.6.2 by setting a default wall thickness in Preferences and then drawing (or redrawing) a wall. Not a great workaround.
I installed v7.5 from SourceForge - it doesn't have this bug.
I assume that setting wall thickness when drawing a floor plan is a simple task that shouldn't be gated behind a pay wall. (But, perhaps I am wrong.)
-= Rich
