It may be required to analyze unmapped reads:
using unmatched reads I was able to perform de novo sequencing and I have some huge fragments of DNA (different set of plasmids, still analyse it)
So, a separate workflow sample can be created for this.
For example, "Filter BAM/SAM files using samtools view" may be used for this, i.e. not to filter reads by a flag, but filter all other reads that do not have the flag. An additional parameter must be added for the worker for doing this.