Is there a way to save custom attributes on a alembic file to read back in Houdini directly from the packed alembics?

No one?

I assume writing alembic userproperties would suit your needs? There have already been multiple threads about it on this forum.
e.g.
https://www.sidefx.com/forum/topic/70783/ [www.sidefx.com]

Thanks for the feedback, what I mean but custom attributes is having to be able to read from points and primitives ordinary attributes like pscale,weight or any custom attributes that you can be carry directly to the alembic primites when you load them instead of just P and path.