Add "tree" / "hierarchical" / "nesting" UI difference depending on the nesting of tabs

[tkr]

I believe that the recent enhancements, such as group tabs and vertical bars, are fantastic improvements! However, I feel that an important feature is still missing: a visual distinction for the nesting levels of tabs.

For instance, when I create a new tab, it represents a hierarchy level of 0. If I open a link from that tab in a new one, it would then have 1 ancestor, and if I do this again, it would have 2. This concept of "nesting" is what makes extensions like "Sideberry" (https://addons.mozilla.org/en-US/firefox/addon/sidebery/) and "Tree Style Tab" (https://addons.mozilla.org/en-US/firefox/addon/tree-style-tab/) so effective and user-friendly.

I suggest implementing an opt-in option that allows users to visualize the nesting levels of their tabs. This functionality could greatly enhance the user experience and organization of tabs.

[Jon]

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.

[ecl]

Yes please. Sometimes a set of tabs don't warrant their own group, but are all related in some way, maybe while still being in a group, so nice to still have a distinction that these tabs under this main/top tab are related. So an informal group or list within a group/folder of tabs.