The key bindings are exactly the same as in the Prolog/Emacs interface. You can compile regions, procedures and buffers; you can search for definitions of predicates (find definition) and you can move around clauses.
To use find-definition in QUI, ensure that a gnuemacs process is running, move the cursor into that window, and proceed as in a straight emacs interface (see ema-emi-key). It cannot be done directly from the QUI main window, so most likely it will be necessary to type in the procedure name and arity rather than select it.
The only thing that is different is that there are no bindings to repeat previous queries to prolog as the QUI window serves that purpose. For a detailed description of the key bindings see ema-emi-key.