Missing new messages due to unclear UI when scroll position is not on top

Description:

I found myself often in the situation where I totally missed important unread messages because my Rocket.Chat (in the web browser) was not scrolled to the top position. There is no visual indicator of that situation.

You can see the UX issue in the following screenshot. There is no unread indicator and there is no indicator that I'm not at the topmost position in the left hand side pane:

The second screenshot shows the very same status but this time, the left hand side pane is scrolled to the very top which now clearly shows an unread message I would have missed in the scroll position above:

Steps to reproduce:

Have a display settings similar to the screenshow below:

1. Scroll down on the left hand side pane such that there is no clipped user name which would indicate that I'm not at the topmost position. This happens to me all the time.
2. Get new messages.
3. You don't realize that new messages have arrived for you to read.

Expected behavior:

I would expect at least one of:

• an unread counter which can't be hidden via scrolling or other actions
• a clear visual indicator of the current scroll situation in the left pane

Actual behavior:

You don't see any indicator that there are unread messages and you don't have any visual clue that you are not at the topmost scrolling position of the left pane.

Server Setup Information:

• Version of Rocket.Chat Server: 3.18.5 (hard to determine! #1111 gave me the hint to use $SERVERURL/api/info)
• Operating System: No idea.
• Deployment Method: No idea.
• Number of Running Instances: No idea.
• DB Replicaset Oplog: No idea.
• NodeJS Version: No idea.
• MongoDB Version: No idea.

Client Setup Information

• Desktop App or Browser Version: Firefox 99.0 64-bit
• Operating System: Xubuntu 20.04 LTS

Additional context

Please do not close UI/UX bugs because they don't seem to be relevant to devs.

Relevant logs:

No source file, test, or entry point is identified in the issue. Start by locating the left-hand navigation pane and its unread-message and scroll-position behavior; done means users can reliably see that unread messages exist while the pane is scrolled away from the top, with coverage for the affected states.