Static Mesh Options
Whether or not to merge the Static Meshes on import (this can cause problems with overlapping UV-sets).
Propagate Matrix Transformations
This will, if applicable, apply matrix transformations to the meshes before merging them.
When importing an Alembic file as a Static Mesh, if your data contains several meshes within it, you can choose to Merge Meshes into a single Static Mesh inside Unreal Engine.
If you uncheck this option, each mesh within your Alembic file will be imported into UE4 as an individual Static Mesh instead of joined together.
Another thing to consider when enabling Merge Meshes is whether or not to Propagate Matrix Transformations prior to merging the meshes.
This will take the transformation data contained within the Alembic file and propagate it to the meshes upon merging so they retain their transform data.
Consider the sample scene created below which we export as an Alembic cache.
When we import the file into UE4 as a Static Mesh with Merge Meshes and Propagate Matrix Transformations we get the following:
If we Merge Meshes but uncheck the Propagate Matrix Transformations we get the following:
Each of the meshes are merged at the 0,0,0 origin.