Not easily. It's best to just use an addon

Exactly what do you want to customize??

Hiding items is relatively easy, but adding items or hiding items which were added by an add-on is more difficult.

Overall, I would recommend using a 2nd Profile with the Menu Editor extension installed to figure out the names of the Menu items you are modifying, by reading the menuedit,rdf file, to come up with the menu item names.

Any menu item that is moved of hidden will appear in that file.

Use the Menu editor add on for right click menu edit. I have used this add on, you can hide or show any time the option available in right click menu.