@Peter Blaise
One simple solution for your needs IS built-in in the “TotalCommander”:
1. go to whatever drive or folder you want,
2. sort for extension (by clicking this above “your” window)
3. press “Ctrl-B” toggles between standard view and listing ALL files (in all sub-folders, too)
– now you can quickly scroll through the blocks with different extensions!
– even better, you can mark some extension and do operations on those files