Note: In 1.5.0 and greater, this is under Relationships -> Subcontrol Options.
Crossfader Overlap is an extension of “crossfader pieces,” which has been a feature of MIDI Designer since version 1.0. You can see that in this video, which is how I fade to a speech track and back:
So the basic idea is that one knob gets spun up to its max, and at the midpoint, another knob starts dropping.
In the past, you set this up by setting each subcontrol be a “crossfader piece,” one of which is also “inverted.” This gives you a linear crossover at 50% of the range of the supercontrol.
For our lighting users, this wasn’t enough, and they asked for crossfader overlap. It’s all linear still (for now), but it gives you some options. Now you can set the overlap to anything from .25 to 1.0. This produces a crossfade that looks like this. Note: Your old crossfader pieces will be changed to .5, which is the standard crossfader overlap.
Setup is almost identical: where “crossfader piece” was located, now there’s “crossfader overlap”:
Here’s an advanced use of crossfaders:
Advanced Use of Crossfader Overlap with 4 Mics on a Field
But the takeaway is always the same: if you want it, you’ve got more flexibility and power for your rig.