Step1: Create an empty project
Step2: Select the item "Use microphone or..." in the picture below, and fill in 1 for the number of tracks to be created.
After clicking Create:
Step3: Drag files, drag files, drag files into the project and check the box "All selected files originate from one project (will create a Smart Tempo multi-track set)" and click OK
Step4: Delete the extra track when you just started creating it. It will be clear by looking at the track name. OK.
