This is my first post in this forum. Nice to meet you!

The following (maybe not Nisus but macOS [10.15.7]?) problem drives me crazy

1. I select text. (A little square is displayed at the end of the selection.)
2. Now I click and hold on the selection to drag it. (The context menu of the little square opens.)
3. I drag, but nothing happens (because the focus is on the context window I never need).
4. So I have to wait several seconds and/or press Esc to close the context window to get rid of it.
5. Then I can drag the selection. Or I can’t, sometimes the context window or square appears again.

Well, I can
1. select,
2. press escape and
3. (without moving the mouse) click to drag,
but it should be possible to deactivate the little square / context window function.
Is it possible? How can I do it?
I never need this square, and if I need a context window I make a secondary click or tap. It would be great if someone would help me see the light … Thank you in advance.