I do not do the glb exporter. The short answer is no, or it would have exported it. Currently, in the .babylon exporter, I only export the keys and no animation, so that is not an alternative
Unless I am mistaken about what non-relate keys are, I am not even sure it directly can be done after load. Not to bore you, but I know that I can do it with my own Blender js generator / animation system. I am not all that familiar with the morph manager in BJS, so @PirateJC here is what he is really asking:
Can you go from one key / state to the next? In my work, I just tell it the key / state I wish to go to, whether that be an exported key or a composite of keys, and an the system takes into account the state it is currently in and morphs from that state to the one requested directly. I am not even limited to putting all my keys in order, like Blender.
I thought if you had 3 keys like he does, (Cube.22, Cube.21, & Cube.24), in morph manager you can only specify what percentage you wished of each at any given time. You can make an infinite # of composite poses from that, but you go from key 2 to key 3 you would need an animation(s) where the frames were like:
0, 1, 0
0, .9, .1
0, .8, .2
0, .1, .9
0, 0, 1
And I am not even sure this would look right in all spots in the intermediate frames.