Technically, the 20 scan lists of the PRO-106 is "more limited" than the 50 "talk group sub-banks" of the PRO-96. However, there is a workaround that might help...
You can put talkgroups from different systems into the same scan list, then enable/disable the TSYS objects.
For example, if you had 3 trunked systems for Town A, Town B, and Town C, and you categorized their talkgroups by Type 1, Type 2, Type 3, etc., you could put all of the Type 1 talkgroups into scan list 1, all of the Type 2 talkgoups into scan list 2, and so on. You might organize the talkgroups in scan lists by usage, geographical area, etc.; hopefully, 20 would be enough.
When you want to monitor a "type" of talkgroup, enable the corresponding scan list. Then enable (or disable) the TSYS objects that are of interest (or not).
Enabling / disabling a TSYS is quick and easy, if you organize your objects with PC software and your TSYS objects are at specific, known locations (Object IDs):
MAN # # # # L/OUT
where "# # # #" is the one to four digit keys to enter the Object ID of the TSYS.