Hi there,
Thank you for reaching out. It seems the issue is at the macOS end. I have shared it with the product team. Once I get a response from them, I will get back to you. Was this working in macOS Big Sur?
However, as a workaround, you can assign custom keyboard shortcuts from within the Illustrator app.
Go to Edit Menu > Keyboard shortcut (ctrl+opt+cmd+k) > Select "Menu Commands" from the drop-down menu where "Tools" is selected by default > Type "Trim View" in the search bar or expand the "View" to reveal "Trim View" > Input your shortcut key combination using (cmd key + any other key) > Click Ok.
Restart Illustrator and the shortcut will start working. I hope it helps!
Regards,
Anshul Saini