Contact List: "Filter by group" subgroup indentation

[sklages]

In the drop-down we currently see:

Otto Warburg Laboratories
Aktas lab
Marsico lab
Mayer lab
[...]

Instead I would like to see such subgroups indented:

Otto Warburg Laboratories
  Aktas Lab
  Marsico Lab
  Mayer Lab
  [...]

That is easier to distinguish/read. lab should be written with capital letter "L".

[sklages]

Alternatively the parent entry may be printed bold - like all other drop-down lists

[donald]

I've made a prototype. Looks like this:

Doesn't really help that the group list is very long and we have several groups where I wouldn't know where to arrange. I have a GUI to sort the groups into a tree but its in django-admin not wagtail-admin, however.

In the current style, the bold is nearly invisible. Plus we don't known what to to with multiple levels...