You can set or update scheduled call-back tasks for leads individually per lead and also in bulk. The changes to leads will then take affect in how your campaign processes the leads.
For example, you can set a range of leads to start being called again at a certain date and time. Or if you allow either employees or your customers to re-schedule call-backs, then you can change them in real-time.
There are prepared API calls and config available as Postman collection to show you exactly how this is done.
First, get the latest postman collection here: Download outbound dialer postman collection
You will see in the collection under Leads folder, that there is a request called "Add callback tasks". This works by specifying the list of lead IDs that you add or change call-back settings for. The JSON body you send will look something like this:
This will set the two leads specified with IDs to start being called on the date-time that you set.
So if you have lots of leads to set to different times, you simply put them into a lists of lead IDs and refire this API request for each date-time setting.
NOTE: you should of course avoid setting too many leads for a call-back at the same time, since these will tend to take priority for some time in your campaign and swamp out leads with other statuses. So use sensibly for the overall campaign setup that you have.
If you want to update other data associated with the leads, the approach is very similar and you can find out how to do that here: Update array of leads in bulk