This runs up against the same API gap as #124 - the need to alter the super-hands state. I've filed #152 to track this.

What's the different behavior that you're achieving here? The current default settings are designed to enable a smooth hand-to-hand pass. When a second hand starts grabbing, the original hand remains in control until that button is released, then then second hand takes over the grab. For example, watch this machinima test

The desired behavior is to have the current hand holding the object immediately release it instead of requiring the initial hand to release first.
I have an experimental feature in hubs right now that lets an object's grab be a toggle- so that if you grab an object, it ignores the next release, but then drops the object on any future release (this maybe should be a feature moved into the super-hands stack, but it seemed easier to do that on the application side for now *see below). It is a bit awkward to have to grab/release a second time in the first hand to pass the object over.

So I see 3 options here:

1. fixing this PR and allowing the option to define the behavior in the case of hitting maxGrabbers limit to either require release on the current hand first or not
2. creating a new PR that allows a "toggleable" grab (which may require option 1. in some form, but maybe not depending on desired default behavior in that case)
3. dropping this PR and hubs can do this purely application side

• I also added an experimental concept that is more closely tied to how our input works, but allows us to specify a "primary" vs "secondary" action in regards to toggling a grab. The idea is that a primary action (e.g. grip button) will always cause the hand to drop on a second grab (in the case of a "toggleable" grab) but a secondary action (e.g. trigger) will only cause grab to start. This ties into the activatable reaction component such that you can, for example, grab a pen with a trigger or grip and be able to "activate" the pen with the trigger without dropping it, then drop it later with the grip.

closing this as I've opted to use a custom reaction-component that copies grabbable's behavior but adds additional functionality (including this).