OK, I now understand that your task templates is not on the same table as your tasks. I did not read your post carefully enough.
So my next question is are you "married" (or at least going steady - I'm sure that kids have new words for that now) to that concept to have the task template records not be on the same table as the tasks. Typically, you would have just 2 tables and not 4. Is it too late to go to that concept or did you have other reason to duplicate the tables.
If you do want to maintain that concept, then yes there is a way to make a button to do that, but it does get way more complicated and would take my as long to explain how to do it than to actually do it. It's probably an hours work for me to set that up for you.