QAC makes entering Test Steps and Expected Results quick and easy. What is not quick is having to change tabs, upload a limited number of files, and specify the mapping for which file should be associate with a particular step. I would like to see this process streamlined and on the same tab as Test Steps.
Perhaps after tabbing past Expected Results, you could have a load file icon which would have the focus, the user could press the space bar, select the file, click Okay, and continue tabbing to enter the next Step and Expected Result. Below is a mockup of what it could look like.