The eyelash is a huge problem when trying to create highly optimised models for Unity. When using tools within Unity to optimise your models, the eyelashes end up as opaque blocks, unless they are given their own mesh and material. This means 2 additional draw calls (4 when lighting is applied). Can you add a toggle/morph to remove eyelash geometry or add them to a separate mesh?
While it is possible to cut them from the mesh, due to the small size of the polys, this is really time consuming and fiddly work. I need to do dozens of these - help!
I ran into this issue as well and the only other answer seems to be out of date or I can't find where the Composer" is in this version. Seems like a faster solution than what I found. I will say I used this solution for other stands of hair as well.
Did some tinkering and found I can hide the eyelashes so they are ignored when exporting.
Click on the eyelashes model.
Go to the Modify Tool and select Edit Mesh
Change to Element selection
Select an eyelash polygon
Click on "Hide" not the option under Display with the eye icon, but the area just above that with the word Hide.