OpenBRF knows those values, because there is an option of mounting on one bone as carry positions, but I'd like to know these values to place my scabbard mesh in exact position in 3Ds Max.
I figured out, how to do it.
1) make scabbard mesh and import it in OpenBRF
2) mount on one bone (in carry position you need), export it as static mesh
3) import this new mesh in same scene with original scabbard mesh from first step, rotate it 180 degrees horizontally
4) use one of scripts for making instances from copies (I use this one]https://www.scriptspot.com/3ds-max/scripts/instance-tool?page=2]this one
5) import in the scene mesh of armour, which will use this scabbard, and in Vertices mode place scabbard from step 2 like you need
6) export scabbard from step 1 (which will be by this moment instanced and transformed) and import it in OpenBRF
If it can be interesting, I can make a tutorial topic with screenshots (for me it was very unclear how to make scabbards with correct coordinates and rotation)