How to open a new container tab using keyboard shortcuts on Mac?

Nico, are you referring to the Firefox Multi-Account Containers add-on?

have you checked about:addons to see if this add-on has been uninstalled or disabled?

If it is still enabled, then you possibly might need to recreate its keyboard shortcuts?

If on the about:addons page you select the Extensions tab then press the "Tools for all add-ons" button near to the search box, there is the option "Manage Extension Shortcuts". Are there suitable options there?

Hi, this is not an add-on, I am referring to the built-in function of Firefox on desktop.

For context, before the update, I also did not use the Firefox Multi-Account Containers add-on.

I think it's provided by the addon and instructions provided by TechHorse above should work.

Nico, I know that you say that you are not using the Multi-Account Containers add-on, but have you ever installed it in the past?

This add-on essentially adds extra functionality for the built-in containers feature, and I am wondering if it was previously added and brought with it the hotkeys that you had been using?

I have a similar problem as Nico, Firefox 151.0.1, OSX 15.7.7 I never installed the multi-account containers. Command-Shift-3, 4, and 5 are OSX system mapped to screen capture, selected-portion screen capture, and selected-window capture function. I don't think this can be changed by the user without some serious hacking. Workaround: Don't use shortcuts 3,4, and 5.