Drag/Re-size Containers?

I would like to break my window up into several sub-containers that the user can easily drag and re-size as needed. This would work the same as how you can drag to re-size the “inspector/library” containers on the right-hand side of the Xojo IDE with the little three vertical line menu.

I thought this would be some type of built-in control since this is both commonly needed and is even used in the Xojo IDE itself (which is built in Xojo unless I’m mistaken). Am I missing something?

imSplitter is Xojo code and open source.

Plugin solution. Seems to perform better.

There’s also GraffitiSplitter