Hi Walter,
We have a feature request for starred channels you can upvote here: https://mattermost.uservoice.com/forums/306457-general/suggestions/11206080-add-favorite-starred-channels
And one for starred messages here:
https://mattermost.uservoice.com/forums/306457-general/suggestions/11679723-starred-messages
We would likely add starred channels by having a star beside the channel name, and when a channel is starred it would be added to a "Favorites" section in the left hand channel list. For messages, we would likely have a star button beside the message or an option in the [...] menu to star the message. When starred, we would probably have a search filter on the right hand sidebar that lists your starred messaged.
If you have other suggestions on how these should work, we would love to hear them - it's probably easiest to comment on the feature idea threads listed above so we can keep the discussion all in one place.
I like the idea of being able to see starred messages in a more organized way than just a list of all starred messages - maybe an easy way to do this would be to allow people to search for starred messages and also use the "in: channel-name" filter so they can view starred messages per channel.