Is there an answer to this question? I am wondering the same.
Thank you :)!
By default, if you highlight or place your cursor on a string and then hit Cntl-R (Replace), it automatically loads that string into the "Text to find:" text box of the dialog. Not as simple as the right mouse functionality you were looking for, but it will get you to the same place.
Thank you for your quick reply :)!! That's a great idea for replacing; will definitely use it.
If you come across with a way of deleting all highlighted strings, I would be interested too :)!
If you leave the "Replace with:" text box empty, the replace will effectively delete the "Text to find:" string.