I put a plugin out the other day that allows embedding of local videos in kirbytext. Works with a single video. I’ve only tested it with MP4 files, but techincally it should work with any valid video.
It comes with a snippet to render a basic player (native browser HTML5), which you can over ride with your own snippet. This the opinionated part. As for previews in the panel, this plugin does not do that but you could perhaps make it happen via the Builder plugin. I could extend the plugin I guess, to include a file method to make that easier, but right now its just a kirby text tag.