Hey Sarah1 - there are quite a few ways you could tackle this in my opinion, but first you'd need to create a segment depending on the goal if it is either "clicked in ANY email" or "clicked in a specific campaign" or "clicked on a specific link within an email":
1. You can create a canvas that will capture users who enter the segment and with a user update step in the canvas you can update an attribute.
2. You can run a Webhook campaign based on the same trigger / segment which will run an API call internally and update the custom attribute.
Either scenarios would work for you, but need to establish what is the criteria for the trigger first.
Best,
