How do I edit the right click menu - items have been added that make the menu extremely long (too long for the screen view) so I have to constantly scroll down to reach an item I need.
It depends which items you want to remove.
The first step is to check in the programs adding the items to see if they have options to hide them, which usually works best.
If they don't, the Opus file types editor can remove things added via the registry, and tools like ShellExView can remove things added by shell extension DLLs.
Opus also has an option to hide all/most 3rd party items on right click menus unless you hold shift or explicitly add certain items back via creating Opus-specific menu items. That gives the most control but is also requires the most amount of effort & technical knowledge to set up.