I've loved using the superb AO #Sidebery in my :firefox_nightly: for many years. Nevertheless i have been keeping an eye on the FF Devs' progress with native #VerticalTabs in #FirefoxNightly over the past several months. A couple of days ago i decided to create a new profile [using the new Profile paradigm in Nightly], into which i installed all the same AOs [except ofc not Sidebery this time], copied across all my bookmarks, passwords, form data etc, to basically replicate my familiar browsing setup except this time with the native VTs & #TabGroups.

I've used this new profile instead of my usual Sidebery profile for the past day, to do all my normal browsing, so i can get a good feel for the viability or not of this native paradigm. Sidebery's hierarchical infinitely-nestable tree-structure is vastly superior to any & all simple flat tab-groups paradigms like Vivaldi, Floorp, Zen, & Chromium... & now also Nightly, but i'm trying to be tenacious & tolerate it so i can make it a worthy IRL comparison test.

However what's highly irritating is the profligate waste of vertical space of these native VTs compared to Sidebery; see pic. Multiple times i have launched the Nightly #BrowserToolbox UI & tried to discover the specific css code controlling the huge padding & excessive vertical height of these tabs, so i can drastically reduce it in my #userChromeCSS... but each time it seems to evade me [i'm not very good at this].

Can any actual Devs or otherwise keen FF UI modders please point me to the code in question?