Create a bookmark in a conversation that you previously processed. You can create a bookmark using a time offset and duration, or by providing a list of message IDs.
If you use a time offset and duration, the bookmark includes all messages that fall during its duration. The offset specifies in seconds when the bookmark starts. For example, assume you have a conversation that runs for five minutes (00:00 to 05:00). A bookmark with a time offset of 20 and a duration of 30 will include all messages that occur from 00:20 to 00:50 in the conversation.
If you use message IDs, the bookmark includes the set of messages that you specify in the messageRefs array.