I only have one hand. Is there a way to make these complicated keyboard "shortcuts" into icons I can put on the taskbar?

FWIW, you could use "Sticky Keys" which allows you to press each key one at a time. To enable them, press "Shift" 5 times. Then press for example "Command", then "Shift", then "3". To disable "Sticky Keys", press "Shift" 5 times again.

You can also just drag "Screenshot" from the Utilities folder into the Dock and click it when needed.