It's not exactly in one step, but one feature that you may not be aware of is the ability to "expand lookup steps". Once you do a lookup, open the Steps panel on the left and click "expand lookup steps" right under the Lookup step. From here, you can click on the Import step and apply changes including hiding columns and group by which are only applied to the dataset that you are looking up against - in this way you can alter the dataset coming into the project before the actual lookup operation. I hope this tip is helpful!