I made a transaction with too small a fee several days ago; hence, it has not been included in any block. Currently, it is lingering in the mempool. How can I use Bitcoin Core to make a new transaction from the same address but with a higher fee? Essentially, how do I do a manual replace-by-fee?
Simply send a new transaction with a higher fee. A miner will more likely include it in a block if the fee is higher.