What do you mean with "Feature flag"? Is it the sling feature with the same name  or do you refer to the software development pattern (which is not tied to any implementation)?
In any way, each workflow launcher has a flag "enabled", which you can set (based on any type of code or automation).
Thanks Jorg for your reply.we have a requirement to invoke workflow based on asset metadata update. For that reason written a launcher which is working fine for individual asset update.
We do not want to invoke that launcher in case of bulk metadata update hence exploring feature enabled / disabled flag option available in launcher configuration.