Hmmm... based on Bookworm_Girl's excellent post earlier, I created a custom column for "long" series and used the sony_collection_renaming_rules tweak to prepend "~":
Code:
sony_collection_name_template = '{category:|| }{value}'
sony_collection_renaming_rules = {'#main_series': '~'}
The good news is, it works - my "main" series collections are separated from the others. The bad news (or at any rate weird news) is, they appear at the END, not the beginning, of the list!
It's not a big deal, but it did surprise me. I still think that the sony T1 is quirky when it comes to sorting punctuation
Going to play a lot more with these tweaks.