Optimize Wallet (GUI)

In the GUI wallet, the command to optimize the wallet is found under Settings > Optimize Wallet

The value you see in the window is the total number of outputs in your wallet. The more outputs in your wallet, the more optimization your wallet will need to send large transactions. If you have less than 100 outputs, then you do not need to optimize your wallet.

When you run this command, it runs several optimization rounds for your entire wallet. You can do this over and over again when you have thousands of outputs or want to send one large transaction, that involves all or almost all of the funds in your wallet.