This is why I love you Phil and I love TubeBuddy as well, haha. Phil, if on the edit video page where you are "inserting" tags, why not just pull that list on a two table pane in tag explorer. Something like this without the background edit video area grayed out. That would allow you to browse tags and manage ones on the video already. Or even split the pane where top area of tag explorer is all the current stuff you have in the tool, bottom half is current tags on video (add a new page below the page break style line under your data sources, above recent).
Now that you're signed up and all, let me know if you have other questions as well and if you want a guide on anything specific? I'm cranking them out every week, but if you have a specific request I'm on it!