We need to create a new member discount that reduces the event fee to $0 when taking the option to pay annual memberships fee. This looks to be quite doable with conditional fields when used with the Base percentage discount option.
Small problem... that option seems to have disappeared :shock:
This seems similar to a problem we have with discounts, both 100% and Amount discount. See our unresolved post titled "Registration process locks up when Discount Code field used ".
The option for Base % is not needed anymore. When you look at the events in the backend event management, there is a column on the right giving a "Fee Order" link. Click that and you will see in that list any discount code that is enabled for the event. It will show the Name of the discount code... not what you type in for the discount, but what the unique name of the code is. Use the drag and drop to move that code into the ordering that will give you the desired calculation result.