SHIFT+A -> Super Parent

Instantly add parent for group of selected objects (keeping current hierarchy)

As a parent you can set Empty Object or sorrounding "Cage Mesh".

Make Parent for all objects in Collection with "Whole Collection" option:

Refit Cage size in any moment:

Experimental - auto refit

With option "Refit Cage Automatically" checked, cages will resize on every change in scene.
Its called experimental as it wasnt tested in scenes with big data, if it influence at processing significantly.

Welcome into the world of Colored Wireframes in Solid Views

You can decide what color have your Super Parent and its wireframe is visible also in Solid views.
From version 4.0 of Blender you can get colored wireframes by default in view settings, but anyway I left this option in the add-on as it works bit differently and still can be usefull (fro example if you want to use colors only for individual objects)

You can change it later in additional Object Properties panel - Colored Gizmo

Additionaly this option is available for every Mesh and Empty Object in Scene so you can  have colored chosen objects in Solid View:

Happy Parenting!