Any smart guesses what I should be putting in there? One end goes to
the three paralleled resistors which are very low ohmage and I guess
current sense at ground, the other goes to the first pin of the
transformer which is at high HT.


another way to figure it our is this...

look up the data sheet for the active devices on the board.

often the data sheet will have schematics for example applications and often the UUT is pretty much exactly like the app notes.

M