Vlad
Orion already supports the concept of tab groups due to its tree-style tab implementation. This is great for organizing tabs, but it needs one small tweak to make it really useful:
Currently, tabs and groups are the same thing. Any tab can be a group and all groups are tabs. This is fine for ad-hoc grouping, but to create a more permanent group, we need a special type of tab called a "Folder". A folder would be a regular tab with an about:blank URL, and the ability to rename it. You could add a folder at any level in the tab hierarchy using a right-click operation, or by clicking a plus folder icon, which would appear next to the existing plus sign, which adds a tab.
So, to give a very simple example, suppose you have a group of tabs that you use at work, and a group of tabs that you use at home. Sure, you could group them into separate windows, but like many users on here, I feel that the multi-window approach is messy and creates clutter, plus it requires additional clicks to switch windows, you end up having to move and resize windows, etc, etc, etc... I hate to use more than one window in any application. From your previous comments in this thread and other related threads, I can see that you don't get this concept; you think it's fine to use lots of windows. I'm not saying that in a bad way, it's just that you think differently from many Orion users. If you implemented this very simple tweak, you could make lots of us really, really happy, without having to do hardly any work.
Instead of having to put my work tabs in one window, and my home tabs in a separate window, I could click the folder icon and create a new folder called Work, then click it again and create a new folder called Home. Again, these "folders" are just tabs that can be named, and that don't have a URL. Now, I can conveniently group all my home tabs under the Home folder, and all my work tabs under the Work folder, and do it all in one window. This would make me super-happy, and I'm pretty sure many other Orion users would feel the same way. The beauty of this approach is that it's already built. You went to the trouble to make a really nice hierarchical tabs list. All that we're asking now is that you take the last step, and make it useful for how we want to work.
Thank you for listening!