Currently right click menu in terminal has terribly defaults in a sense that rightclick p does not cause paste since both Preferences and Paste have that as shortcut(underlined letter in command name).
So when I do right mouse click and press T I get a new tab, but when I press P it does not do paste since P is not unique, so I need to press P and then again P since first selection is Preferences, then finally I can press enter.
How do I unbind Preferences totally, or at least just give it another unique shortcut key?
Paste in Ubuntu Gnome terminal already has a shortcut, it is Shift-Ctrl-V.
If you forget it, you can see it in the edit menu above, see image.
Image showing edit menu
Amending Diaa Sami's answer with some background. As far I understand, the concept is the following:
Shortcuts (also called Hotkeys or Accelerators) are typically global to a window, invoke a certain action without having to open the menu. Their purpose is to significantly speed up the execution of certain tasks. The keybinding is shown in the menu next to the action. It can include one or more modifier keys, and the chosen letter doesn't have to have any correlation with the action. The predefined shortcut keys typically don't vary across languages (e.g. usually Ctrl+N stands for opening a new something even in languages where the word "new" doesn't have this letter – at least within Latin scripts). gnome-terminal allows to redefine the shortcuts in its Preferences dialog.
The underlined letters in menus are called Mnemonics. My feeling is that their primary purpose is not as much to speed up pasting or other similar actions for the average user, but rather to make everything on the UI a bit more easily accessible, including for those who have problems using a mouse. I find it more like an "accessibility", or "efficiency for those who need accessibility", rather than an "efficiency" feature. I might be wrong with this impression, though. Anyway, mnemonics are local (specific to a menu/submenu or a dialog), and have to be letters taken from the action's wording, otherwise the underlined notation couldn't work. Mnemonics are hardcoded, and vary across languages. It's the translation who picks the mnemonic for localized versions. In English maybe opening a new tab has a unique letter while pasting shares a letter with another action; in some other language it could easily be the other way around. That being said, developers and translators of a software should ideally aim for unique mnemonics, it's just not a high priority goal and sometimes conflicts like this sneak in.