New release.
Now, Rectify, Rotate Island ±90º, Align World, Align Edge, Select Overlapped, Select Bounds, Select Flipped, and UV Smoothing support multi-object UV editing.
Some fixes (rectifying of edges/vertices) and cleanup in Rectify.
Rotate Island ±90º was failing depending on the version of Blender, now it works.
Select Overlapped now is faster and more accurate, using the Blender builtin operator.
Select Similar renamed for clarifying.
As always, it should work from Blender 2.80 to the latest stable 2.91, and as far as I know, works in 2.92 with the latest nightly build as well.
Download from here:
https://github.com/SavMartin/TexTools-Blender/releases/download/TexTools_2.92/TexTools.Blender.2.8x-2.9x.zip