Support XEP-0333: Chat Markers
When using multiple clients, e.g. Conversations on the phone and Gajim on the computer, the phone will often show notifications for messages that I have already read on the computer.
The phone currently has no way to know that I read these messages on the computer.
There's an extension, XEP-0333 (https://xmpp.org/extensions/xep-0333.html), that clients can use to tell each other how far the participants of a conversation have read. Conversations already has support for this XEP. If Gajim were to implement support for Chat Markers, then other clients connected to the same account would know when messages are read in Gajim, and can take appropriate action (e.g., remove notifications).