Yes, you can absolutely reinvest your earnings on HEXN.
Once you receive your payout, you're free to use those funds to open a new savings position. Just make sure the amount you reinvest is equal to or greater than the minimum investment threshold of 90 USD (or the equivalent in your chosen cryptocurrency).
Additionally, if you’ve enabled auto-renewal on any of your active savings, they will be automatically extended under the same terms and conditions you originally selected - no need to take any extra steps.
Reinvesting is a great way to compound your earnings and make your crypto work for you.