We are "researching" for the setup of our next virtual conference. Ideally we would need to have a separate channel per each talk/poster. That would make it into thousands (to see our quickly hacked up poster session solution at https://datalad-datasets.github.io/ohbm2020-posters/#/ - that is where in each "poster room" we want its mattermost channel embedded for a chat). Having a hierarchy would provide a solution to organize. e.g. have something like

ohbm-2021/
posters/
1
2
..
talks/
1
2
...

so I would greatly welcome this feature!

Even one level of hierarchy would help. I have more channels at the office than I can fit on screen, and it's hard for me to tell when notifications are for goofy things, urgent things, or directed personally. Getting them all into a few folders would make that possible.

Check out how Discord does it, or a smartphone app group.

For example the Git Client SmartGit just uses "/" to collapse or expand sub branches

Yep sounds very good. Voted for it.

This should be trivial, and it's a core function that's needed.

This seems to have a ton of votes... wondering if it's been considered ever. Would make a huge difference for our teams.

I suggest to allow a special character in chanel name, like '/', who would act as a separator.
Then, it's just a matter of interface.that would allow a sub grouping of chanels with the same 'prefix', inside or outside the already implemented hierarchy (private/favorite/public/etc...) by a simple option.

I think this issue should only be visual, at first.

Each group needs to be collapsible as well. imo

This is ABSOLUTELY ridiculous to don't provide a way to group/structure elements if more than 7-10 in any context, any application

If this gets implemented, it would be an opportune moment to add the ability to reorder channels

This will improve the efficiency of mattermost greatly.

There is a way to implement this feature with minimize modification.
My suggestion is special treatment on the string of group name.
For example : The original groups are shown as
group1::topicsA
group1::topicsB
group1::topicsC
group2::topicsA
group2::topicsB
group2::topicsC

Modify the display behavior based on the special treatment on the string "::"
group1
+ topics_A
+ topics_B
+ topics_C
group2
+ topics_A
+ topics_B
+ topics_C

That means what you need is modifying the client app and web plugin.

+ 10 votes if I could.. Mattermost seems so 'basic' :( I hope people who paid for the entreprise version have something but then it's sad to not get it in community version

definitely like the idea of organising the channels but wonder if a more appropriate way would be via tags and filters. Different people in my organisation might have different ideas for how they would like to view their channels.
Or is that just a completely separate feature?

Yes, this would definitely help organizing the channels and make my work-life a lot easier!

As well as improving presentation this would also allow us to join to the top level channel and have an option to automatically join sub channels so, for example, a projects team manager subscribed to the top level "All Projects" channel can participate in all sub-project's channels under that parent without having to join the sublevels individually

I also need this functionality in the company. Otherwise we cannot use Mattermost in a satisfactory manner. Is this functionality on the roadmap for a next version?

+1 for me

I would be greatly interested in adding this functionality, but first am looking for some approval from the Mattermost team.

I have done a brief mock-up, and imagine it could look similar to this:
https://i.gyazo.com/f0fcfe878fc1dd66430b85e8d5a3946c.mp4

This was all done using HTML5's details and summary elements.

It seems to be similar to [zulip](https://zulip.org/)'s channel model. They are called stream.

Maybe a hierarchy of channels separated by dots that allows folding of the tree does the trick:
e.g. folded you see:

+office

and unfolded you see:

-office
office.fra
office.ams
office.lon

This could be followed for multiple subtrees:

- office
- office.lon
office.lon.news
- office.ams
office.ams.news
etc.

Or is there an even better approach?