I use QAP and end up with tons of DOpus tabs open. I frequently close them via r-click the tab I want and choose "Close all other tabs." Is it possible to make a toolbar button for this?
I looked in Customize --> Commands --> Folder Tabs. There is a "Close Tab" command, but not "Close all other..."
You can use GO TABCLOSEALL. Also, the documentation for this particular case it's on here: Go [Directory Opus Manual]
You can close all tabs to the right or left with Go TABCLOSEALL=right or Go TABCLOSEALL=left
For me using 13.6,
I already have in the tab menu, close left or close right.
Manual for Tabs default
Thanks folks. I should have pointed out that I did find the tabs contect menu. That's how I knew the command existed. I just didn't see how to make a button. It looks like the answer is [EDIT] updated the answer, after reading Leo's tutorial linked in his reply below.
Right-click an empty spot on the toolbar and choose Customize from the context menu. Then, again, r-cllick on a toolbar and shoose New ---> Button. Then r-click that button, and choose Edit. Then paste in the GO TABCLOSEALL. Then I dragged the new button to the location I wanted and closed the Customize stuff.
Thanks agan. -steve
You don't usually want a User Command, and definitely don't want WSL Script Function for this. 
See the first part of How to use buttons and scripts from this forum for quick instructions on how to make a new button for a command.