Well, I think I'm giving up on this one... I haven't found a reasonable way to accomplish what I'm trying to do (and I have to pick my battles with limited time these days).

As an alternative, I've installed shortcutd and am using the camera button for bringing up the dashboard. It's a lot more sensitive than I'd like, but at least it solves the problem.

If I stumble over the info I need, I'll update this thread with the new code I come up with.