There is no way to enter spam referrers directly. Piwik, sorry, but is being slow about updating the referrer list. It would be great to enable manual entry as it was before.
Afaik the spam list is updated once a week.
There were already some requests to trigger that manually: Allow manual update of referrer-spam-blacklist within Piwik admin · Issue #9380 · matomo-org/piwik · GitHub
To suggest new entries for the list, please create an issue on github: GitHub - matomo-org/referrer-spam-blacklist: Community-contributed list of referrer spammers. Comment +1 in any issue or Pull request and the spammer will be added to the list!
Historical data won’t be cleaned after an update atm, but maybe that will be possible in the future.
See Feature to delete historical referral spam · Issue #8404 · matomo-org/piwik · GitHub
To delete that manually, maybe that might help you: Let me delete Visitors from Visitor Log (and undo it) · Issue #3385 · matomo-org/piwik · GitHub