Is it possible to add new items under the sandwich button?
Yes there is!
DBarranca has a great tutorial on his blog on how to add elements to the flyout menu. He also made an example project so you can take a look at how he implemented it.
Check them out.
PS-Panels-Boilerplate/src/com.undavide.flyout at master · undavide/PS-Panels-Boilerplate · GitHub
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