Don’t know if by now there are solutions out there for this (I haven’t fully kept up with this subject for a while), but I finally found a way to trigger the actual cockpit switch (including the 30s buildup) with a StreamDeck button. I got it working by using AxisAndOhs which can discover and read LVARs and HVARs. There is indeed an LVAR for the switch (XMLVAR_InertSep1_Switch), and by using AAO’s Streamdeck plugin you can easily map it to an SD button, works great!
There also seems to be an LVAR for AP Trim (and maybe others), haven’t tried this out yet but that’s the next I’m going to look at.
Dirk