When a piece of text is highlighted with the mouse, it can be pasted by middle-clicking on the place you want, or by using the always classic
Shift+Insert key combo.
But, when the area where that selected text is closed, the paste option is not valid, since the copied text is deleted.
Where is exactly the ready-to-paste text stored? Why is dependent on the application where you grab the text from instead to store that piece of text anywhere else, e.g., in a place of the memory with no relation to the source of that highlighted text, and keep it there even when the application is closed or another text is selected?