Meta Ads - campaign optimization by conversion event

Hello, We managed to integrate events from ManyChat with my ad manager, for example, the purchase sent from a workflow, now I'm hitting a wall since those events that I return to Meta Ads cannot be used to optimize a message campaign. For example, if you generate a campaign that has the objective of sending an Instagram message (DM), you have no way to optimize the campaign for the event that we send from ManyChat, making the return from ManyChat to Meta Ads useless. Has anyone found a way to give value to the events?