Something like this may work:

export const selectXX = createSelector(
  [
    (state: IRootState) => state.xx.A
    (state: IRootState) => state.xx.B,
    (state: IRootState) => state, // <-- add input selector that returns entire state
  ],
  (A, B, state): IViewerSpace[] => {

    if (A == null || B == null) {
      return [];
    }

    const args = { A, B };

    const { data } = designRTK.endpoints.getData.select(args)(state);

    // ...some transformationlogic
  }
);

But using a selector function that just returns its input or just returns the entire state object could have negative effects and is not generally recommended. This implementation will likely re-run anytime the Redux state is updated.

There’s a dependency on the selected/derived A and B state.

I suggest splitting up the logic to make the returned “A or B” selector value an additional argument passed to a second selector, the UI will need to call both.

Example:

const selectXX = (state: IRootState) => state.xx;

const selectXXA = createSelector(
  [selectXX],
  xx => xx.A,
);

const selectXXB = createSelector(
  [selectXX],
  xx => xx.B,
);

export const selectAandB = createSelector(
  [
    selectXXA,
    selectXXB,
  ],
  (A, B): IViewerSpace[] => ({ A, B }),
);

In the UI:

const aAndB = useSelector(selectAandB);
const selectXX = useMemo(() => designRTK.endpoints.getData.select(aAndB), [aAndB]);

const value = useSelector((state: IRootState) => {
  const { data } = selectXX(state);

  // ...some transformationlogic
});