I have all the pre-loading software for detecting GMST's, but is there a program that can tell if you have already introduced them into a save game file?

Because 1) save games only save changes to data & 2) GMSTs can not be changed during play there are no GMSTs in a save game file.

Ah I see.
I remember someone talking about "introducing GMST's to a save game" a while back, so that's where my concern's came from.
Thank ye.

You can check active plugins for most of the "dirty" GMSTs in-game. E.g. for the Bloodmoon GMSTs, open the console and type:

player->addspell bm_summonbear
player->addspell bm_summonwolf
player->addspell bm_summonbonewolf

Then check if the creatures show up after casting the spells.

But as already said, this can be corrected at any time.