Apple - How can I remove "zombie entries" from login items when the controls are dimmed?

It's far late, but I have discovered today, trying to remove a similar zombie item that you cannot remove items for ALL ITEMS when the padlock icon is closed. Open the padlock for any action that involves other users. That's all.

The (All Users) is a clue that the system has been instructed to make all users have this item and it's not something you would add or remove from a user account.

You could browse to /Library/StartupItems and just remove the Bamboo (or potentially Wacom) items by moving them to trash or uninstalling the software that put those items on the system.

To be complete, if there are other users on the Mac, they may need to re-add that program if they want to use it.

Seems you don’t have permission to remove this item — are you on a restricted account? You could try to launch System Preferences with sudo, and then try again. Open Terminal, then type this:

sudo open /Applications/System\ Preferences.app/

You will have to enter your user password (which is not shown on screen).
Let me know if this works!