I'm going to say that most (though certainly not all) flavorings may be PG based, (but I mean heck some are alcohol based). If you need that percentage I'd input as PG whatever amount of flavorings you are using as PG, i.e. if you add 10% flavoring, for the most part it will be accurate enough in MOST cases. I have some VG based flavors but by the time I get around to inputting every possible flavor variable in some of my mixes, l think I would lose my mind entirely.
I would just say count flavors as PG to your overall total and unless you and your vape are SUPER sensitive, or SUPER OCD, well, I think you'll be fine. I don't have that issue but I am PG sensitive and hence, I just count all my flavorings as PG only and don't go much above 10% flavoring which is perfectly fine for my purposes, and ensures I won't be creating something intolerable, although to be totally honest, even if I WEREN'T PG sensitive, I'd probably do that because in the grand scheme of things it's close enough to count in my eyes and etc.
Anna