Hi Niko,
Can you clarify what you're trying to do here? This will help us answer you better.
Brainstorm supports having multiple conditions and runs per subject, so splitting your first subject as Subject01 and Subject01_2 is probably not required. Head models can be copied from one folder or subject to the next if they have the same anatomy. Right click on the head model -> File -> Copy, and then right click on the destination folder -> File -> Paste, or use CTRL + C and CTRL + V.
Best,
Martin