Yes. I sort of figured it out.  2 of the plugins conflict on the left mouse button mapping:  line profile and labelpainter.  Other plugins such as threshold work fine as there is no conflict.  https://gist.github.com/tinku99/cd39bfed85e6bafcedf7a390e51c2430 

I can probably just setup a different keybinding to get the line and label painters to play well.

> I would also recommend looking at Napari, which is a great platform for doing visual data inspection.

Thanks, Stéfan. Yes, will check out napari.