Github user joewitt commented on the issue:
https://github.com/apache/nifi/pull/2671
If you take a look here
https://nifi.apache.org/docs/nifi-docs/html/administration-guide.html#core-properties-br
and checkout the 'nifi.nar.library.directory' section you can see how someone
could be guided to create a directory for custom nars, add that in there, and
start up.
Once we have support for extensions in the NiFi Registry this will be
beautiful/easy.---
