Sorry, I thought because you said "I enabled "Highlight in Documentation" option" that you wanted a highlight to appear. If you tick that box then the highlight automatically appears in the top right corner by default and you have to move it manually...
The default location for a document highlight is in the top left of the screen. In order to move or resize it to highlight the correct UI on the screen, you need to choose the red box at the top of the screen "Document Highlight" and once you are hap...