I’d really like to be able to create a single sitemap that can then be included in multiple questions in a tree test. When you have 10’s of questions it means having to create the site map 10’s of times. And it’s even worse UX when you have to edit those sitemaps. Optimal workshop does this feature very well (as an example).

There is no need to create the sitemap again and again on every tree testing block.
Once you upload the Sitemap into the first Tree Test block, you can duplicate this Tree Test block.
The newly created Tree Test block will incldue the Sitemap that was uploaded in the Tree Test block that you dulicated.