Back when Moodle 3.2 (or so) was released and I switched to the new Boost theme, I had noticed that the right blocks could not be collapsed. There was a good amount of discussion about this (see https://moodle.org/mod/forum/discuss.php?d=341576#p1387015 ), including some good thoughts from Martin and others in Moodle HQ.
I created MDL-57305 as a feature request.
Well, good news, Daniel (and Gareth) has worked on this feature request and have made some very good progress. We now have a working example, maybe even a solution. I see that Gareth has continued with code that suggests additional ways to implement this feature.
Based on Daniel's code, I made the following video to demonstrate what I was looking for.
I am making this post to encourage folks to vote on MDL-57305, where Daniel's fix has added this feature back into Boost, and he mentions that the core code exists but had been removed from the Boost theme. I would like to see the code back to Boost.
I welcome additional ideas.