After you've made an allocation you can change the reward recipient address by clicking on the icon next to the recipient address
In the pop up window, specify the new reward recipient address and click Confirm.
If the new address already has an allocation, no problem - the vault will automatically combine the two.
Changing the Amount
To change the amount allocated to a recipient, click the icon next to the amount.
In the popup window, specify the updated amount for this reward recipient and click Confirm.
If you reduce the amount allocated, then the undistributed rewards are reduced in proportion. For example, if you'd allocated 1000 MATIC and there are 5 MATIC of rewards that are undistributed, changing the amount to 500 MATIC reduces the Undistributed Rewards to 2.5 MATIC.
If you increase the amount allocated, the vault treats the additional amount as a new allocation. For example, if you'd allocated 1000 MATIC and there are 5 MATIC of rewards yet to be distributed, increasing the amount to 1500 MATIC is the same as adding a new allocation for 500 MATIC starting now. Rewards in the future will be the 5 MATIC earned up until now plus the rewards now accruing from staking 1500 MATIC.
Deleting an Allocation
You can also delete an allocation completely by clicking the icon on the far right of the row.
After checking the details in the popup, clicking Confirm deletes the allocation. Any undistributed rewards will not be distributed.