BlendMode

section	GL
short description	sets some blendmode variables and changes the render
licence level	Anjuna
ports	Input [gl/render]
	Output [gl/render]
	AlphaCV [control] – most likely this is to input a colour value which is to be set to transparent
parameter	Alpha [knob/rotary fader] – to set the transparency level
	SrcBlend [dropdown select] – the source blend mode
	DstBlend [dropdown select] – the destination blend mode
skins	./.

The possible options for the blend modes are hardcore GL details. As an entry point you might start here: https://www.khronos.org/opengl/wiki/Blending.

Manual

Applies the specified blend modes to the input GL render signal.