Ashley said in 2014, when introducing the new Multiplayer Objet;
-We have plans to add even more features, ranging from persistent logins with player data storage, to geolocation-based matchmaking to help improve the connection quality.
is it me or the persistent logins with data storage was never a thing?
imo it makes multi limited if we cannot store things for every player... like in a rpg for instance.
Since not a lot were using it and demanding for it. It didn't get improved.
Then again, there was a time it was in demand and failed but it was Construct 2, it didn't have as good support unlike now with subscriptions. But now with Construct 3, people mostly gave up on the multiplayer plugin and went for the alternatives like customized plugin, customized back-end, WebSocket System or 3rd party plugins like Colyseus or Photon Cloud / Server.
To be honest though, if you plan to have Multiplayer for your games,
I suggest making your custom backend + client plugin for massive CCU per room games like IO games and use Photon for Battle Arena Games.
For online data storage, I don't think relying on the Construct Team or Scirra is recommended. I'd use Firebase for that or a Custom Server Database.
If you don't have any programming background:
For Realtime Multiplayer::
Battle Arena :: Photon
For IO Games::
I guess you can use the Socket.IO plugin, I think there are some free ones here. Or better yet, buy a utilization license or hire someone to make you one.
For Online Storage Database::
You can use the Firebase Plugin by Rexrainbow.
If you have some programming background:
You can make your customized backend + plugin client and mix in with other 3rd party plugins. It makes things easier in the long run and you have more control and flexibility for performance, storage, bandwidth etc...