Facebook doesn't provide native methods for hiding most of their side panels and other assorted annoying page elements, luckily there are third party methods to do such things, a browser add-on I use and trust has many such options for hiding the annoying parts of Facebook you just wish would all go away. Facebook has complicated matters lately because they ...
I made a tampermonkey script for this:
Re-pasting here if easier:
// @name Slack tab title asterisk remover
// @namespace http://roman.chernobelskiy/
// @version 0.1
// @description Permanently keeps the asterisk out of slack's tab title.
// @author ...