Is there any way to enable it for admins but not any other user? I’d like to be able to test it out and adjust my forum layout (once it hits stable) before making it public.
The other option is to set up a testing instance but if an easier option exists I’d prefer that.
Not at this time. We plan to support for appending a query parameter to do this kind of previewing in production. For the time being a staging site is the available alternative.
(we support ?enable_sidebar=0 (or 1) to override the enable sidebar site setting, but don’t have a similar one yet for the enable experimental sidebar hamburger site setting, which is what you need in your case)