Syncing up quick actions and labels/milestones in new issue/merge request pages

Problem to solve

When a user creates a new issue or merge request, they can add labels/milestones via quick actions and the respective dropdown fields. This leads to problems if you choose one milestone via quick action and one milestone via the label. It also does not give you a correct overview over how many and which labels will actually be added to the issue/merge request.

Proposal

As a first step, we could sync up the two different methods. If I add a label via quick action, it will get added to the label dropdown. If I choose a milestone, it will get chosen as the milestone in its dropdown. There are details to be figured out, e.g. what happens if I have chosen a milestone via quick action, but then update the milestone in the dropdown. Will it get removed or changed in the quick action?