I know this has been discussed a lot in the past, but it needs to be said again. A lot of us would like to edit the HTML file directly and yes I know you can use costume code blocks or convert to HTML but its an absolute hassle and a lot of people would love this feature implemented. There were rumors in 2016 that this might be a feature but we heard nothing yet. Bootstrap-studios is already a great software but this feature would make me and probably everyone else use it a lot more for bigger projects.
you can edit CSS in your favorite editor. And there's a new command panel in 5.1x. The new editor supports a emmet-like syntax too. Still there won't be a direct import-export feature for HTML. But things are slowing going better and better. And soon we hope BSS will be a multiwindow app, so the editor will be usable on a different monitor too.
that said I agree with you, it could be a nice feature, but it's not on the roadmap. And I understand the developer reasoning about potential problems and code quality