Haha, I will probably be similar when I hit the 10-year mark! There's a lot to learn, and although I don't dislike the UI as some people do, it means certain 'hidden' functions get left by the wayside. So I understand.
The key is to take modulation input not from any LFO or ENV, but rather from the other VCO (I think maybe self modulation by the same VCO is possible too). So, the target VCO acts as the carrier, and the source the modulator - thus equating to a sort of 2-op FM (well, phase modulation probably!). Then the FM Depth is some odd combination of DX7-style pitch ratio and modulation index that I've not completely figured out.
I tend to use my actual FM machines instead, but I did make one or two basses a couple of months ago; maybe I'll remember to upload those another day. :)