I find them unnecessary and confusing. Luckily, they can be easily disabled with the right bit of magic. The only tricky part (which I’m not going to cover here,) is getting root shell on your device.
Once you do have that root shell, issue the following commands in it:
pm disable com.facebook.katana/com.facebook.katana.activity.media.CameraLauncherActivity pm disable com.facebook.katana/com.facebook.katana.orca.ThreadListLauncherActivity
The first disables the camera shortcut, the latter the messenger shortcut.
You can issue either or both, depending on which of the shortcuts you wish to remove.
To reverse the process, and restore the removed shortcuts, reissue the command(s) again, replacing disable with enable.