For example, in the Toucan example, there is a subnet to set initial pose of a rig by modifying its parms detail attribute:



But that's 5 nodes. Is it possible to wrap them as a HDA, but still exposing the APEX Scene Animate's viewer state to top level, so I don't need to dive into it every time?

I haven't tried but I might be possible by promoting Scene Animate's hidden(?) "stash" parameter to the top-level and then setting its viewport state to apex animate (see how the Autorig Component SOP HDA does it).