First-use observations: good things, Dialogue closing and Light issue

[rccDave]

First, thank you for taking on this branch. I have not used this tool much but like what it can do, so far. Images now load, which is what brought me here in the first place. I also appreciate the use of system file system browsing.

When trying to close some dialogue boxes with the upper right "X", an error would be raised. I cleared the log and continued.

Moving the light does not seem to work with Middle mouse + L.

There are a couple dialogs that could use a "Default" button. I think Post Process was one (and there was another somewhere; I'll watch for it again next time).