Solaar is a Linux GUI manager for Logitech mice and the small USB receiver which is used to connect the mouse to a computer. This receiver used to be device 1 on my Logitech MX Master mouse. At some point though, I forgot that device 1 was reserved and paired a laptop via Bluetooth. Logitech has their own software to fix this and repair the receiver with the mouse, but this (predictably) runs only on Windows and Linux. Solaar fixes this: The GUI is intuitive and I was able to repair the mouse and my receiver in about 5 minutes. Great! (No more 30 second delay after the PC starts up until the mouse starts working => This is not consistent, but sometimes, Bluetooth connection simply does not work and I have to forget and repair the mouse.)
Caffeine is a GNOME Shell extension which can be used to temporarily disable the screen lock and idle setting on a Linux machine using GNOME as the desktop environment. The screen lock can be disabled by directly going into the Settings utility as well, but Caffeine makes this super simple by adding a Coffee cup icon to the right side of the sticky top bar in Gnome. Click this icon, and auto-lock is temporarily disabled. Click it again and it is re-enabled. Open a video in full-screen and auto-lock is automatically disabled and re-enabled when you leave full screen. A very useful tool!