Maybe it’s already too late but in order to help other people having the same question, here is the answer, coming from the FAQ:
Revolut currently supports card payments and ATM withdrawals in over 140 currencies wherever Mastercard and Visa are accepted.
There are only a few currencies remaining unsupported, including: ZWD, CKD, KID, PND, TVD, AMD, FOK, ERN, BTN, EHP, CUC, SHP, GGP, JEP, IMP, SDG, SYP, IRR, PRB, SOS, KPW.
You can currently only hold and exchange between USD, GBP, EUR, PLN, CHF, DKK, NOK, SEK, RON, SGD, HKD, AUD, NZD, TRY, ILS, AED, CAD, HUF, JPY, MAD, CZK, QAR, THB, and ZAR on the app.
Meaning that you can exchange HRK but not hold it from my understanding.