It probably goes without saying that pinning can also be easily accomplished with a hotkey, but I still think it’s worth mentioning. While using the hotkey is quite easy, I can imagine that the double click method would be quicker if you wanted to pin a few tabs in a row. Maybe it could be a setting, enabled or disabled in a special section of the hotkeys customizer. In fact, I just created a feature request that would be a perfect place for this type of behavior to be set: Modifiers/clicks/special behavior section within Hotkey editor
It is curious that double clicking isn’t used for anything as of yet. Perhaps double clicking a tab is being reserved for yet another awesome Obsidian feature long in the works.
Thanks.