Elastic Search FSCrawler

I need to add custom field FSCrawler index json. Can we add custom field ?

See https://fscrawler.readthedocs.io/en/fscrawler-2.5/admin/fs/rest.html#additional-tags

Can we modify _id field elastic search json while indexing ?
I need to put my custom id instead default.

Look on the same page for Document ID