Ability to see painted masks
I haven't found a way to do this yet, but it would be helpful if you could hover over a mask and the mask is shown on a bigger window, or even being able to see the black and white mask on the model. I just want to be able to see the black and white mask I painted, and right now the mask icon is so small it's hard to tell what's going on.
Just do alt click on your mask to display it on your model
Fortunately for you, this is actually a feature in Substance Painter. To preview your mask on the model, simply hold down ALT and then left click on the thumbnail for the mask. This is display the mask on the model so you can better see how the mask is looking so far.
To be fair, it's one of those features that's not too obvious unless you know it's there in the first place.