Thank you for this update! I appreciate your community-oriented approach and the preliminary designs are looking really nice - it's good to see that you are considering native support of plugins like Sidebery and TST!Aside from my feedback from earli...
Consider me a bit biased, but Sidebery along with this userchrome is a really great trade-off between having an unobtrusive tab interface along with behavior a user would predict of their tabs. Other vertical tab implementations (Edge, Floorp, Vivald...
I don't even think it needs to be a second sidebar - just a way to easily (with GUI) have multiple sidebar applications, like how Vivaldi/opera do it. though a second sidebar would be nice too. I'd put my calendar on there in a heartbeat
