Is there a property in 'Chat' object of Team Messaging chat that can be referenced to Mark Chat as Read or Mark Chat as Unread?

Hello,

our development team is trying to implement Mark Chat as Unread functionality.

From the response here https://community.ringcentral.com/questions/114789/how-to-enable-mark-chat-as-readunread-api-post-req.html, I understand that Mark Chat as Read/Unread API calls are not yet implemented, but one more question remains:

looking at the object of Chat in Team Messaging API Screenshot 2023-04-04 at 10.07.47 AM.png

I don't see a property which I could reference when I want to decide whether the chat should be marked as unread or read. Could this property perhaps be lastModifiedTime (I suspect not), or is there going to be a new field implemented in the future in 'Chat' object that will indicate when the chat was viewed the last time?