Also looking for this feature, I found this thread as well as a previous one here https://forum.freecadweb.org/viewtopic.php?t=11424
referencing another issue created before http://freecadweb.org/tracker/view.php?id=2498
I cross referenced the issues in their comments in the tracker.
This would be a great feature addition IMO too because compounds make a powerful way of grouping parts but being unable to add/remove members/children is a pain along the design path. Having to explode/delete then re-create them several time is a burden, and this becomes hardly doable when you have a hierarchy of compounds.
Anyway, thanks for all FreeCAD goodness