Select

shortcut dbl LMB

The Select tool is used to quickly select all decals of one or more parent objects.
It's simimlar to Blender's object.select_grouped(type='CHILDREN_RECURSIVE', however, will only select Decals, instead of all children.

Selection

Any number of objects carrying Decals.
Any number of decals.

Note

For multiple objects, you want to double click on the background, otherwise you will deselect one of the objects.
Also, for users of the 2.80/default keymap, I suggest changing the keymap to something else, because selecting on the background will deselect all objects.

Using Select

Properties

Keep Decal Parents Selected

Adds the Decal objects to the already selected parent objects.