How to set up sign-magnitude in signal editor

[Urbanmelon]

Hi, I'm in the process of going though data on my '04 Volvo V70R and learning about canbus. I found the steering angle signal and figured out how it's encoded but can't figure out the correct DBC options.

The steering angle is two bytes organized like so:

• bits 0 to 14 is an integer, scaling is 0.045
• bit 15 is the sign bit

My understanding is that this means it uses sign-magnitude as opposed to two's complement. Is sign-magnitude supported? Right now I have to split the sign in a separate signal to get readable data.

Thank you!