Models fields dialog: Picker usability issues

[nilshoerrmann]

Description

As mentioned on Discord today, we noticed two usability problems with the pickers in the panel:

1. The selection indicator has a rounded outline which usually refers to a single select (radio input) although multiple items can be selected from the list (checkbox input).
2. The selection indicator is aligned to the right which a) makes it harder to scan the selection and b) disguises the function of the arrow which is not related to the selection but the navigation of the item's children.

I've been in video meetings where this posed a real accessibility issue (editors didn't know how to continue, how to navigate and how to select) and I've been confused by the picker myself in the past, too.

Expected behavior
Switching to the new page tree component as @distantnative mentioned on Discord might be a good choice.

Screenshots

Your setup

Kirby Version
Kirby 3 and 4.