creating dropdown menus within a cell

Krayziez,
Lists work for any worksheet in the file. So, you could have a separate worksheet called "lists" and put all your lists in there, name them, then use them in any other worksheet.
Or, if you don't want to have an extra worksheet, put them off to the side somewhere and then hide (highlight, right-click, hide) those columns so they're invisible.

Autocomplete works in Excel, so using keystrokes to enter information in the drop-down menu cell should work once you've entered that information once. It will work much better if your list items all start with a different letter, instead of P1, P2, etc.