When a track is selected, this custom action behaves just the same as the one you already know and love on Control+T, IE, it'll create a new track, give you a chance to name it, the new track will slot in underneath your current position in the tracklist and your selection will automatically be set to the newly inserted track. But, if you run this custom action with a folder selected instead, then it'll slot the newly created track in underneath the folder, as opposed to the usual behaviour of inserting a track into the folder. It requires SWS and OSARA. Here are the components:
SWS: Select only children of selected folders
Xenakios/SWS: Select last of selected tracks
Custom: insert and name track