Activate the Appearance Editor and add a Scar that either gets applied to the Head or Arm.
Right click on the Scar tab in the Modify panel and select "Move to" from the menu. Click on Body.
The Scar is moved to the Body and can be adjusted and duplicated to achieve the effect that you want.
System: Win 10 Pro (20H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-452.06), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.