http://sparrowa7io5pz6ud3ehqzosvepbxbxt2zphmkjsylp2zgxooko23pqd.onion/docs/faq.html
A transaction’s fee can be increased either by replacing it (RBF), or creating a child transaction (CPFP). To perform Replace by Fee (RBF), the transaction must: Be in the mempool (not yet confirmed) Have all inputs enabled for RBF (this is the default for transactions sent by Sparrow) Have all inputs from your wallet If all the above is true, then Sparrow will add a hover icon next to the transaction on the Transactions screen which looks like a hand with a cross above it.