It's VERY easy to disable the codex of wisdom. I did it 8 years ago when I first started playing, even before I started using UOAssist.
Go into the UO (not UOAssist) macros. Define the F1 key as whatever you like (I did mine as saying "All follow me"). Apply. Close the macro gump, then reopen it. Click through your assigned macros to make sure your new meaning of F1 is the only one present (deleting any others).
and the Codex is gone from F1.
As long as you don't click the button to revert to defaults, you're good.
Also, look for the the box for passing the keystroke info to UO, in each UOA keybinding.
Usually, you DON'T want to pass the keybinding on, for anything not one of the basic 36 keys (A-Z, 0-9).
However, it's possible to create some nice double-macros (a combination of a UOA macro and a UO macro, running at the same time) this way, such as one to disarm and rearm in UOA, with a potion use timed (using delays in each) to occur between them.