You can give your users the ability to add more goals to their open goal sets. This is done through the event type settings.
To allow people to add more goals to a goal set which is in progress find the event type for which you'd like to enable this in. Within the field settings for the embedded goal you will have already enabled custom goals as shown below.
Allowing custom goals enables the person creating this event type section to specify what the goals should be at the time of submission of that section. Beneath this are individual settings which give the ability to add/edit/delete further goals to the set created at the time of submission of the event type section.
You can additionally choose from any of the roles within the system to set who should be able to perform the add/edit/delete actions on these custom goals.
Add new custom goals - further goals can be added to the goal set whilst it is still in progress Edit custom goals - the title and description of the goal can be modified. New targets can be added to the goal and existing targets can be modified or removed. Delete custom goals - the entire goal can be removed, including any associated targets.
The ability to add/edit/delete goals cannot be given for predefined goals.