readr::write_tsv help says that the function will take
A data frame or tibble to write to disk
but assumes that the columns are all vectors. Each of your marker rows is a list, presumably of character vectors. Those need to be unpacked. The simplest way is to treat each as a single string
That's doable, but you'll need to right pad out each with trailing \t so that the number of tab delimiters on each line match the number in the longest. Otherwise, other applications may choke trying to import.
Could you post a representative gene_name and marker? Use