Blender add-on for managing groups of objects (collection instances).

For Blender 4.2 (or newer)

With GroupPro you can merge objects into one container object in non destructive way (using instances collections). Features:

edit any group (collection) instance on scene
work in recursive way - group, can be created from subgroups, which can be made of subgroups etc. Any subgroup can be edited and saved, with all other instances updated in real-time
easy mirroring of selected groups (fixes group instance mirror bug in blender)
change group origin or apply transformations, without destroying positions of other instances placed in scene
dissolve group (split it into original objects) - with option to create (maya like) empties hierarchy
edit material in all group sub-objects in one click (replace, add, assign mat)
create group proxies (temporary lowpoly version, to speed up viewport)

Pros of using group instances:

GroupPro comes with build-in auto-updater - get latest version with one click. See updating Documentation.

Here is video showing new features GroupPro 2.3

You will get free updates whenever there are new ones.