Isn't putting every cell in its outline sufficient?
This is strand 305. I moved the "push" cell to be a child of the "split" cell, used the split cell and moved the second "push" cell in position. That uses up all my moves and every cell is in its white outline. Why doesn't the game accept this solution?
A solution cannot contain any special cells, including "push", "split" and "destroy". Also, a solution cannot contain any cells outside of the outlines.
This means that you will have to expand those "push" cells and still find a way to fit your strand into the outline.