It’s very tiresome for having to “choose” a cell, by double-clicking it, or pressing f2, so just after that I select text as any notepad editor does.
Your wish does not seem to be possible with Calc. That may be because Calc is not a word processor. I suspect you have the wrong tool for your desired task. You describe a single function, but unfortunately not what you want to achieve overall.
Just copy cell at once by Ctrl+C and you’ll copy any text from the cell. Then you’ll can paste it into any software
That’s not at all what I want.
Selection of text like a notepad, if it’s possible at all, is something pretty simple.
but why is like in the notepad?
In a notepad you don’t have to double-click to enable text selection.
If you want notepad functionality then don’t use Calc, use Writer instead.