Slitherine

Is there an easy way to see who has claims against me?
Thanks.

Go to Ledger -> Authority, sort by claims against player, press Shift + 7 and click on the nation. Region they have claims on will be highlighted by red in your territory.

Thank you.

Another question. What is the best way to get them to give up a claim? I tried diplomacy and they wanted so much that it made no sense to do it. Thanks for any opinions.

Beating them in war is a popular war.
Also preventing it by improving relations is a way.
Improving relations make it cheaper too. But cost something in improving the relations.

Improving relations
Gift from diplomacy, cooperation, giving them very good conditions on other trades.