Custom sort ("Light-table") will only work when files from a single folder are displayed. (Right?)
In other situation it would be less confusing if the custom sort option would not even be selectable.
( I had (files from) two folders displayed when I discovered this)
This depends on how you display the folder. I'm not sure tight now, but you can still sort "per folder". If you of course also disable the hierarchy, IMatch has no way to store the settings. I just made a test and it worked.