Well, I was pressing some shortcut keys and then this happens. Was this an existing feature or my tinderbox got updated? (9.1.0) (Check screenshot)
Command-7 toggles this on and off. Has been a feature for a little while now.
My note indicate the Links Panel was added in v8.6.0 (see here), back in March 2020.
Further to @latinhypercube’s point, the default for displaying the Links panel is ‘off’ (i.e. hidden), so you don’t normally see it. Your shortcut experiments likely including pressing ⌘+7. The Links panel can also be toggle on/off via the app’s Window menu.