Ctrl+Tab cycles forward, Ctrl+Shift+Tab cycles back. You can also change the behavior with the about:config preference `browser.ctrlTab.sortByRecentlyUsed` for either tab strip order or recently used order...
Well I would suggest implementing at least at the level of modern desktops, and make it easy to find and use it, not just alt+tab shortcut. Ideally it should be spawned and allow the user to filter to find tabs instead of having to hold and release a key. My point being, a simple forward/backward cycle is definitely on the lower side of effort when it comes to window management (tab management), which to be honest is not a problem to me personally, but I find the gap left there on purpose bizarre and makes me question it. I don't think browsers should consider themselves just rendering frames since it is the interface that users use, it's not a component, and it should be (very) ambitious when it comes to advanced features, especially with something as fundamental to them as tab switching.
Just to make sure you're aware, there's the Firefox View feature which lists Open and Recently Closed tabs, sorted by parent window, with a search box for filtering. Navigate this page with mouse or keyboard (Tab and arrow keys). It also lists History by date or domain.
There's also the List All Tabs feature, which has been available a long time. Either or both of these can be added to your toolbar from the Customize Toolbar page.
I guess anything more sophisticated could be done via add-ons.
Is there a browser you feel does a better job of tab switching?
I was aware of those tab listers, though I use my own addon. However the motivation to make this thread in the first place was because I was in fast-switch mode, going back and forth between tabs, to copy/paste stuff etc, and I kept feeling stuck, my mind was expecting something as intuitive as a taskbar icon, and the "alt+tab" available didn't even cross my mind tbh and a cycle is not that great, there's a reason an OS like windows doesn't just cycle without previews on alt+tab. I don't know what other browser does this better. I make my own tab manager, check out Grasshopper on the marketplace, I've been adding all the task switching features there. That moment was just that my brain was wired expecting something else and the browser felt incomplete.
And while we're at it, I want to focus the fact that browsers never evolved beyond maximized tabs instead of venturing into windows. At least the modern ones.
What are you proposing?