Hi
I had a couple of hiccups and a tiny issue with the otherwise excellent UV Master plugin. Nothing worthy of showstopper status but nevertheless here they are.
1 ) If your model happens to have polypaint where Materials are embedded, this will be carried over to the new tool when you press the Work On Clone button. So if I have a nice metallic material embedded in polypaint, which works well for my model, I do not necessarily want that material when I am trying to paint protect/attract zones or while viewing the seams. I know, a small issue but easily fixed with color filling the tool with the Flat Shader material.
2 ) If I have loaded the same tool twice there is a problem when pressing Work On Clone. For example, loading ZSketch_68_5.ztl twice and pressing Work On Clone will clone the first loaded ZSketch_68_5 AND all its subtools. Not sure what is going on but the renaming of the current tool when Work On Clone is pressed looks suspicious, a “” is added to the name. Sometimes a “CL_” is added to the name when it is in fact the original tool and not the clone.
3 ) Just a personal issue I guess. Some of the button name pop ups are awfully long are they not? I mean, some of them fill the entire width of my monitor which was at 1600x1000 
Which brings up another pet peve of mine. Would it not be better for zplugins to use the CTRL key to bring up extended information on a button, just like with regular UI items? Much better IMO than ZPlugin authors adding “hold ALT for more” to the button name or simply displaying the entire button description in the button name pop up. And while I am on the subject why does holding CTRL + ALT reveal a different button description compared to just holding CTRL ? Oh go on, please tell !! 
In any case thank you again for the UV Master plugin. Very much appreciated and it has already shown its worth as a time saver. Thank you.