How to Enable Auto-Resize for Split Windows?

How can I enable automatic resizing when splitting two windows 50/50 on one screen?

I want to be able to adjust the size by dragging the center line between the windows, so one enlarges while the other shrinks automatically. Right now, they just overlap. I've checked the settings but can't figure it out. Any advice?

if you are on macos 15, this is now the default behavior. Place your mouse between the snapped windows, then you can drag to resize. On older macOS this is not possible

I am a bonehead! I wasn't trying it directly from the center! Thank you