A few keywords can be set up at a time.

https://www.evernote.com/shard/s132/nl/14501366/209a66f1-3cdb-4192-b8f0-c60fc5bb1c15
Now mandatory keywords can be designated by the "+" sign.

https://www.evernote.com/shard/s132/nl/14501366/209a66f1-3cdb-4192-b8f0-c60fc5bb1c15