Question on computing niche cell type composition

[ankitbioinfo]

Dear developers,

I have a question regarding computing niche cell type composition from following tutorial. https://scenvi.readthedocs.io/en/latest/tutorial/MOp_MERFISH_tutorial.html

I have two spatial dataset where one has corresponding scRNAseq but another one does not. Can I run envi for both dataset to get similar plot like in step 153? If yes then what modification need to done.
Also why FDL_COVET and DC_COVET need to transfer from both spatial dataset to scRNAseq at step 21-24. Can I compute cell type composition without COVET part?

Thanks and apologies for asking layman questions.