[Feature request] Display entries without group assignment

[okunze]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
I would like to have a possibility to display entries without group assignment in the group selection.

Currently I can select “All” or created groups, but I have no way of determining which entries are not assigned to a group (unless I look at each entry individually).

Describe alternatives you've considered
N/A

Additional context
N/A