Is it possible to split a BLine (to remove a segment of a BLine)?
Not possible. You can delete vertexes but the BLine will continue being continuous.
Alternative: Duplicate the layer and delete the vertexes in each BLine to obtain the two separated portions in two layers.
It could be a nice feature to be able to do that automatically, even with animated BLines.
Another alternative - you could hide a section of the bline with an ‘alpha-over’ blended region.