@sambeth
The hash (#) character is reserved as a delimiter to separate the URI of an object from a fragment identifier.
Registry has a number of different fragment Identifiers. The fragment identifier represents a part of, fragment of, or a sub-function within, an object. The fragment identifier follows the "/#/" in the URL and can represent fragments in text documents by line and character range, or in graphics by coordinates, or in structured documents using ladders. For example the "grid-list" of flows displayed when you access the NiFi UI.
No, you cannot remove the # from the URL. Are you encountering an issue?
Hope this helps,
Matt