Feature Request: Allow persistence of vertical tabs (sidebar.verticalTabs) across sessions

[birajkalita008]

Currently, when I enable vertical tabs within a PWA session, the layout successfully switches. However, upon restarting the PWA, the extension forcefully resets the UI to a horizontal layout. I attempted to hardcode the following preferences via user.js in the isolated profile directory:

sidebar.revamp = true

sidebar.verticalTabs = true

browser.tabs.inTitlebar = 1

Despite this, the extension's startup script overwrites these preferences, reverting the tabs to the top. I understand this might be a deliberate safeguard (possibly related to Issue #667) to prevent crashes with the new Firefox vertical tab architecture.

I would like an option—either as a toggle in the extension dashboard or by allowing user.js overrides to persist—to permanently enable vertical tabs for specific web apps. A native-feeling PWA often benefits from a vertical sidebar, especially on modern widescreen displays.

If vertical tabs are currently disabled strictly to prevent crashes in the current Firefox release, I wanted to put this request on the radar for when Mozilla stabilizes the vertical tab API. Thank you for building such an incredibly useful tool!

[filips123]

Yeah, it's because of that crash, and I still haven't had a chance to properly fix the issue. Unfortunately, currently just adding an option to allow verfical tabs probably wouldn't work, because it would still cause a crash or other issues (from quick testing, it seems that at least for me, it doesn't crash anymore, but is still not very usable as you can't access widgets and buttons from the now hidden taskbar). I still plan to properly fix it, but maybe I'll wait until the Nova redesign is finished, as that will probably also require some changes.

Also, I'm curious what would you like to use vertical tabs for? I guess it would only be useful when you combine it with the (existing) option to show tabs in the web apps, right? Just so I know the expected usage a bit better, so I can maybe make the settings more intuitive. And when the vertical tabs is enabled, the toolbar, showing the window title, widgets and control buttons should probably still be visible, like normally (when tabs are disabled)?

[birajkalita008]

Hey Filip, thanks for the update.

My main use case is AI web apps like ChatGPT and Gemini. I use the tabbed mode so I can keep multiple chats open inside the same app window instead of mixing them with normal browser tabs. Launching them directly from the desktop also feels much cleaner.

I mainly prefer vertical tabs because they save vertical screen space, especially with the hover-to-expand behavior.

And yes, I’d only use this together with the existing “show tabs” option enabled.

The top toolbar should definitely remain visible though, mainly for normal window controls. Keeping the overall UI minimal would be ideal.

Waiting for the Nova redesign before properly implementing it makes complete sense. Appreciate you looking into it.