Hello, and thanks for the great suggestion!

This is already possible in NuFi wallet; you can unstake and withdraw a partial amount from an existing stake account (e.g. an amount equivalent to your staking rewards) without needing to stop staking. As you said, this happens by splitting the stake account in two and then withdrawing just the part containing the custom amount you want to unstake.

To do this, find the stake account in question (in your Solana staking dashboard), and then click the 3 dots on the far right side. You'll see the option to Unstake.

Untick the box that says 'unstake all' and you'll be able to enter a custom amount to unstake and then withdraw.

Open a support ticket if you need any help: https://support.nu.fi/support/tickets/new