Editor-powered Unity Object drawers will have no control for adjusting the width of their their prefix column.
This is similar to how the default inspector works.
Always Top Only (Default)
A control for adjusting the width of the prefix column of Editor-powered Unity Object drawers will be placed right below the header, above the body of the drawer.
This is a safe option to choose, as it guarantees that there will be no overlap with content drawn inside the Editor that might span the whole with of the inspector.
Using this option also makes it easy to spot drawers using Editors, as they’ll always have that distinguishable resize control positioned below the header. This instantly lets you know when some of the enhancements offered by drawers might not be usable.
A vertical line will be drawn through the whole body of Editor-powered Unity Object drawers for adjusting the width of their prefix column.
Note: The line might overlap with GUI elements inside Editors that span the whole width of the inspector!
Most Editor-powered Unity Object drawers will use the top-only control for adjusting the width of their prefix column.
However in cases where we know that Editors contain no GUI elements that would overlap with a vertical line drawn between the prefix column and the controls column, we will switch to using such a vertical line for adjusting the width.