MacOS – How to switch tabs using keyboard on bigsur

There are quite a few commands which let you do this in Mac OS X:

Cmd+Tab for switching applications
Cmd+` for switching windows within applications
F3/F9 for Exposé (shows all windows in a graphical way, on trackpads you can do a 4-finger swipe down)
F10 for showing windows of a specific application in Exposé
F11 for showing desktop and shoving all other windows to the side, on a trackpad its 4 finger swipe up

There is also Spaces which is like having multiple desktops, where you can switch to and fro. You can enable it in the Exposé & Spaces prefrence pane in System Preferences and suit the keyboard shortcuts to you liking

You can do this via Terminal's AppleScript interface, for example to set the background colour of the first tab in the first window to green:

tell application "Terminal"
    set tabsettings to current settings of tab 0 of window 0
    set background color of tabsettings to {0, 32768, 0} -- colours are 16-bit
end tell

That's the good news. The bad news is that the background opacity is not exposed to AppleScript in Lion (this seems like an oversight by Apple). You can change pretty much everything else like this though (see the Library in the AppleScript Editor for the full list). There are a few crazy AppleScripts out there that adjust the background opacity by emulating keypresses to Terminal, but that approach is too horrible to even link to.

Once you have the AppleScript code to change the settings to your liking there are many ways of binding your script to a key.