The vertical tab sidebar is a pretty cool feature, and I think adding a few notable functions to it from the Tab Outliner extension in chrome will make it even better. here is an example of how I use tab outliner in Brave:
You can see here that there are many grey tabs, which are turned off (they don't show up in the main tab bar). I can open up any of these tabs by simply double-clicking them, and as a bonus, they will maintain the order in which the appear within the tab outliner
In this way, the tab deactivation feature acts as a more elegant version on the bookmark concept
Additionally, the notes are very handy for organizing the tabs. There are notes that act as your run-of-the-mill folders (because they are nodes in the hierarchy), but there are also notes built into the names of the tabs themselves (very handy for giving them permanent names because the title is not always reliable, and it's nice to see the color distinction between my note and the title of the tab)
Orion's vertical tab feature is already most of the way there. you just need the notes function, and you need to make suspended tabs turn grey to indicate a deactivated state (which is a sensible thing to do anyway) ...
Do this, and Orion's tab implementation suddenly becomes superior to the tabs outliner extension (especially when you take into account the already-existing profile segregation and multi-device syncing that tabs outliner does not handle well)
For those of you who might suggest fixing tabs outliner in Orion (which is not currently working for me), I wouldn't consider it a priority, because I actually WANT this to be a native function of the browser ... precisely because it will benefit from the profiles and multi-device syncing that i mentioned above