I spent some time in 2.79 recently. You cannot drag from all 4 corners there. Being able to split or merge from all 4 corners is essential to the joy of life. Having a drag indicator in the corners is nice but having it permanently visible in all 4 corners of every area would be overkill.
What if the indicator only appeared gradually as your mouse got closer and closer to the sweet spot:
As a new user mouses around the UI for the first time they will have at least a 25% chance of indicating the hover effect within a few seconds and then be tempted to click and drag.
If the cursor had a tool tip saying “merge or split editor areas” then they should have an easy time with it. And I mean a REAL tool tip.
[Moderation note: Removed screenshot from other software]
What if we split the action into 2 steps.
Step 1: Drag from the corner.
A preview overlay shape that is never more than 25% of hovered editor area appears in either the upper, lower, left, or right of the hovered area.
Step 2: Release left mouse button.
The mouse cursor position jumps to the center of the edge that can be moved.
Step 3: Move mouse to set the desired size of the new editor area, then click left mouse button.
Right click or ESC key can be used at any of the steps to cancel.
I think clicking a corner and moving inside the existing editor should just do a regular split, like it works currently in master. When I click a corner and move horizontally, I want a vertical split. As you have it now I have to think too many thoughts and observe too many things instead of using muscle memory.
Clicking the corner and then moving outside of the editor should trigger your new feature.
I’ll try to make a video tomorrow demonstrating what annoys me the most. Making a new area from a current area and resizing it at the same time in one motion is something I do a lot.
Moving an existing area to a new location is definitely something I want but not at the expense of the first thing.
In the following situation I want to move the outliner to be to the right of the shader editor and let the properties take the full window height. Your build is great for that. But to get into this situation in the first place with your build is annoying compared to the standard splitting behavior.
I thought they were vector files and infinitely resizeable.