Can be enabled by the MSTS way: BrakesEngineControllers( "Independent, Train, Dynamic, Blended" )
There are two new parameters for Engine ( ) block:
-OrtsDynamicBlendingOverride ( 1 ) eng parameter makes dynamic brake lever always override blending command if, the lever is not at 0. If this is not enabled, the higher command is applied, for example: blending command is 40% and the dynamic brake lever is at 60%, then the dynamic brake percentage will be 60%.
-OrtsDynamicBlendingForceMatch ( 1 ) parameter makes the dynamic brake blending alorithm to try to achieve the same dynamic brake force as the airbrake would have (in case of bailoff)/ or has. for example: if the airbrake force would be 28 kN, then the dynamic brake force will try to hold the same force.
The dynamic brake blending uses "virtual cylinder pressure" so the bailoff, does not affects it, so you're free to use that.
Brake_Dynamic block (which defines dynamic brake lever) is not needed to make blending work, as there are locomotives that don't have DB lever, but have blending.
Example eng for Acela HHP

Number of downloads: 335 (note, acela has a very narrow dynamic braking range, which fades completely over 100 km/h)