I believe if you change the subject of the email/thread when replying, a new thread will be created. This should not be exclusive to Mail or Apple’s services, and should also work in at least Microsoft Outlook, regardless of the client (OWA or app)

@SmoothC@lemmy.world this may also help you

⌥⌘C

Another tip:
In the Edit menu in Finder, hold down the ⌥ key. You will see Copy “myfile.png” change to Copy “myfile.png” as Path Name. That is how I got the keyboard shortcut.