[Layout] Enhance UX to manage margins of an app

[Julien-Dubois-eXo]

Is your feature request related to a problem? Please describe.
In the edit layout I can manage the margin of the app. However it's not explained that the margin setting is shared with the other app next to it. When I reduce the bottom margin of the top app, the value is not updated on the margin of the other app. I see 2 different values when it's the same in fact.

I have nothing that explained to me it's a common margin.

Describe the solution you'd like
First, it could be interesting to indicate that it's a common margin.

• Maybe updating the label to a clearer one, i.e. "Common label"
• A link on the label to open a drawer with an explanation of the settings

Second: link the settings of the app next to another. When I edit the margin of one app the margin settings of the other app is also updated.

Explication.marge.commune.mp4

[srenault-meeds]

My suggestion:

• No more pixel identification for each app to avoid this confusion (20px, etc.)
• Instead of it, we propose to the user to add margins or to remove margins
  That way, it will be more understandable for users that they can add margin to the top of an app to extend the margin between an app and another one.

WDYT?

[Julien-Dubois-eXo]

Why not, for the moment I use this feature only to remove the margin.