Logitech mice and keyboards have extra features that the OS would consider non-standard; you can customize a lot of behaviors as well as map extra buttons to specific actions. For some reason, Logitech decided not to store customization settings on-device so there is a background daemon that must run on the host. Also inexplicably, it is an electron app with a 600MB install footprint requiring online connectivity (apparently there's also an offline version, weighing in at 1.2GB). Also not available on Linux.

You usually don’t _need_ it but there are a couple things you can’t do without it. Pairing a mouse/kb to their usb receiver for example is not possible without it.

I use the Master MX 3s specifically because of the "gestures" button, it was mandatory for me to replace using the trackpad. It's basically a thumb button you can press and combine with a mouse gesture to do the same thing as finger gestures on the trackpad. I mainly use the gestures left/right (to switch between full screen apps/main dektop) and up (mission control) but it's all configurable. It also has an horizontal scroll wheel that's very useful when using Excel or DB viewers.

I much prefer a mouse (I use the MX Vertical) to a trackpad for long periods of time at my desk.

Cmd+Scroll for zoom in/out, Ctrl+Left/Right arrows to switch spaces. It's not a fun as the trackpad, but those are things i don't do that often.

Looks like this is for the "Logi" high end office series. They use different software for some reason, I guess Logitech thinks their customers don't want to see anything gaming related in their app because it looks unprofessional.