Extensions make Firefox a lot more useful. For some extensions, it's especially useful to reach them through the context menu that pops up when you right-click with your mouse.
That usefulness, though, can get eroded if you wind up with too many options on the context menu. That happened to me. I wound up having to right click, then scroll through the context menu to find the tool I needed. That's a pain.
The problem is that Firefox extensions often add themselves to the context menu whether they're useful to you there or not.
The solution? Edit the menu. How? With another extension.
If that sounds counter-productive, consider this: the extension you'll use doesn't add itself to the right click menu. In fact, it doesn't even add itself to the Firefox Tools menu. It just sits in the Add-ons dialog box waiting for you to want it.
The extension is called, appropriately, Menu Editor. You can get it here. See Extending Firefox if you need help.
Once it's installed, go to:
Tools > Ad-ons > Menu Editor > Preferences
There's a drop-down menu to select the menu you want to edit. If you choose Main Context Menu, you'll see all of the items that can be on a context menu.
I say "can" be on a context menu because there are actually a few different context menus depending on where you are when you right click. That's the "context" part of "context menu."
You'll get the significance of that when you see how many menu items there are. You probably don't see them all on any one menu, but they're lurking.
This makes designing your menus a little hit or miss. I hid a couple of items that I later added back on.
Tip: Before editing your menus, right click on a web page and see which of the menu items are useful. Do it in a few different contexts, like on white space, with text selected, on a tab, etc. Make a list of the items you want. That way, once you're in Menu Editor, you'll be able to quickly hide the items you don't want. It's amazing how many items wind up on the menu. I didn't remember some of them until I started editing the menu.