Each time you create a new address, it is recommended to backup its private key in case you lose access to the wallet.dat. The QT wallet doesn't display the private key unless you follow the below steps:
Go to the "Help" tab in your QT Wallet and select "Debug window".
Go to the Console tab, and enter the following command -
dumpprivkey <your R-address>
Note that this command will only work for addresses that are owned and within your wallet.dat
If you have encrypted your wallet.dat, it will need to be unlocked before you can export the keys. Follow this guide for details - https://support.komodoplatform.com/en/support/solutions/articles/29000024698-how-to-encrypt-your-komodo-qt-wallet
If you face any issues, please join us on Komodo Discord to talk to our community.