I suggest to have 'Mark read' option for any Channel in Mattermost.

There may have few groups which are integrated to get notification of JIRA updates or Jenkins to build status. Loads of messages are received there and one will see notification icon until one open that channel.

It will be great if Mattermost provides 'Mark Read' kind of function to clear particular channel notifications without opening channel chat.

I would recommend having this as a right-click option of a channel.