That was very helpful indeed.
I doubt that anything more could be said about how one goes about gaining accessibility inside Windows Sandbox. I don't use it, and it is clearly a VM-ish sort of environment, but it behaves even more like a true VM than I had suspected. It appears you get a perfectly "clean slate" on invocation and must do any necessary setup each time.
Brian - Windows 10, 64-Bit, Version 21H1, Build 19043
The ignorance of one voter in a democracy impairs the security of all.
~ John F. Kennedy