Is there any way to have Zbrush auto-update the texture file when alt+tabbing back from photoshop?? Wasn’t this functionality previously in zbrush?? If it’s not in there, where would be the place to request it being an option for those who desire that functionality??
They took it out in 3.0. 
There is a wishlist thread on here (ZBC) I’m not sure who started it or if anyone is looking though.
Aurick might know where to properly submit requests to Pixo for their review.
You could always use the support center I suppose to ask.