Task Manager can be accessed via the Bottom-left Menu OR via Rt Clk on the Taskbar
I had never seen the Task Manager on the Taskbar. I just never paid attention.
Whenever I wish to access the Power Users menu I simply use Win + X. It seems quicker for me. There is a wealth of stuff on this menu. No need to drill down to it in a Start Orb any more. Task Manager is just one of the 15 items plus Desktop that are available in this simple to use menu.
I do not know a whole bunch of keyboard shortcuts, just a few simple ones I do all the time. Actually, people that use their PC's professionally usually have learned the keyboard keystrokes for doing their work as they seem to think not leaving the keyboard is quicker than using the mouse.
Complete System Specifications: By Speccy