If you are using TextGrabber on an iPhone, tap the three dots in the upper left corner, which will open the utility menu. There, tap the button to the right of the “Close” icon. That is all — the text will now be copied to the clipboard. You will also receive an additional notification about this in a pop-up window.
In the note view window in TextGrabber, tap the “Share” icon in the upper right corner. The button you are looking for is located there and is called “Copy.” That is done — all the text has been copied to the clipboard.