I like the tab-switching behaviour in Chrome/Firefox and wanted Safari to have something similar. Another wish of mine was for it to be a web extension that feels native to the browser vs an app extension that looks out of place.
After waiting long enough, I decided to build one myself. A little preview of Tap Tab. The web extension APIs for managing tabs are pretty locked down in Safari, but I have already found a lot of value in using the extension. Some of the features that I find very useful(in the middle of building a few of these) :
Say hello, and tell me what features you would like the extension to have!! You can follow the updates on Twitter.