For those like me who struggled to figure out how to get counts data for hashing antibodies in .obs, the below link is helpful. This step is necessary for demultiplexing antibody hashed samples by hashsolo program.
My fastq files were processed through Cellranger 8.0.1 where I provided information on TotalseqB antibody barcodes as well as Hashtag barcodes. That is the reason I had antibody counts in .X layer of my muon data or mdata which I needed to transfer to .obs of filtered_feature_bc_matrix file.
If my understanding is incorrect, please feel free to correct.