If i am correct by left navigation menu of Designer studio, you mean "App Explorer".
I have created an activity and then done a withdraw for this activity and after doing a refresh i cannot see it in the app explorer of the designer studio. I have tried this in 7.1.6. Please refer the attached screen-shot.
Could you provide the version where you are trying to do this.
I had a look into this requirement internally and I see that it is still under development. I suggest that you keep a watch over the relase notes of the future releases! I too will help keep a watch and update this thread if I get to know of any developments.