Add ability to have columns inside each tab in the field layout editor

[thupsi]

Hi!

I seem to remember that Brandon mentioned this as a possibility further down the road but I can't find the relevant discussion, so here goes:

The 'width' attribute for fields in the layout editor is great, and, together with the more recent addition of the 'line-break' UI element, provides flexibility to field layouts. However, it still is not possible to achieve all layout configurations without 'real' columns, meaning columns that are containers for the fields inside a given tab.

The layouts that are more problematic are those with matrix fields that tend to get long and 'push' other fields further down the page. Currently, there is no way to have more than one field (one below the other) beside one such matrix field. There are of course many other situations where having containing columns would be beneficial.

I'm attaching a mockup that shows a proposed UI for adding such columns to the field layout editor:

Of course, the columns could have a 'gear' icon for access to settings, such as title etc, and there could be an additional button alongside the 'add column' one, called 'new row', 'column break', or something similar. Also, it goes without saying that the width selector for fields would be constrained or discarded according to the containing column width.

As always, I would greatly appreciate any opinions on this. Thanks! :)