Show relation collections in the fields column

I like to visually hide fields by being able to make them only appear in the fields column.
So to hide them but not disable them, and not use their collapse function since that still takes up space and distraction in the main center fields area.
To keep the entity display clean, I like to be able to make them appear only in the fields sidebar, and make the fields sidebar hidden by default. Clicking to show the fields sidebar will then also show the fields that I find secondary in importance.

Ideally, the fields sidebar and the center fields display would function to remove secondary fields from the visual area of the entity, and any field (incl properties and relations and collections) can be configured to show up in either the center fields area or the fields sidebar.