You can delete a goal (without closing your entire Endowus account) by following these steps:
Redeem the entire investment portfolio for the Goal: You can do this by going to the Invest/Redeem tab > Redeem > Select Goal > Select Account(s) > Check the box for full redemption
After the entire investment value for the Goal has been redeemed, you can go to the Dashboard > Goal > Goal Settings > Select Delete Goal
Please note that you can only delete goals which do not have any pending and/or processing transactions, and do not have any investment value.