stop automatic split screen for windows (not Windows) and…OOPS!

Possibly in the new version of MacOS?

i open desktops in separate windows. i want to put 2 or more desktops together in one window. Click, hold, and drop works on some, but not on others. They are windows that have an automatically generated split screen. I can move the splitter from side to side but that’s all. (I can’t show a screenshot so I'll explain it.) It’s like when you’re on zoom and you split the screen to show a page of…. you can move the splitter to see the page larger or move it in the opposite direction to see all the participants.

How can i stop automatic split screen?

and...

(I can’t show a screenshot b/c it doesn’t work. ANOTHER problem to fix.)

"Your screenshot can’t be saved.

"Cannot write file to intended destination."

I know i did something i shouldn’t have. "too smart for my britches”. In case you’ve never heard that, it may be from another era for you, I’m 76

How can i reverse my mistake?

mac mini

apple m1

16G

mac OS 15.3.2

HD 114GB available