Hello @icenov there isnt unfortunately an easy way to delete the nodes at the moment via a similar API.
If your happy to sort them via the database, here are the steps:
mysql -u emoncms -p emoncms (password: emonpiemoncmsmysql2016)
DELETE FROM device WHERE userid = 1;
exit
redis-cli flushall
then refresh the interface. This assumes the account you wish to delete devices from is userid=1