First turn on coin control so you can send from specific inputs. My current goal is instead of staking with 500 addresses, to stake with 500 inputs on a single address.
Select what inputs or addresses you want to send from. In this case I have a large single input I want to spread out.
Specifiy the address that exists in your QT wallet to send to. Checkmark Split UTXO. And type how many inputs you want to spread out to. After that, right click the after fee amount and paste into send amount.
Wait for the transaction to have 10 confirms and you are done.
Use https://www.coinexplorer.net/D to check your address, then click See Address Unspent Outputs to see your new inputs getting ready to stake.