I managed to apply morph targets in the sequencer as animation blends (drag drop in the timeline sort of thing).
I created a dedicated morph target animation in my 3D program (say, morph blinking at 100% keyed for one frame at the first frame with no other animation) and when I import that I make sure the morph target animation uses ‘Local Space’ in the characters Animation>Asset Details>Additive Settings>Additive Anim Type pulldown (otherwise the bone animation will also be applied in sequencer, even if it’s the T/A pose). After this (if I recall), I could drag this animation into the sequencer on a different track, or even the same track as other bone animations, with full access to transition etc.
Update : If Local Space doesn’t work, try Mesh Space. I have found that this works and I can combine skeleton animation and Blend shapes (even multiple if needed).
It’s not ideal And there are some limitations, I would also like access to morph targets track in sequencer, but we do what we can Hope this helps!