(comment was edited)

Show the drawer using this button:

Click the + to create a new server

then you should have different versions in this dropdown:

Thanks very much for taking the the time for me @cappert....I thought I was going insane there for a while! 😄

So directly after installation, I had to find the reveal side-bar button in order to find the plus button. It might be an idea to just have the sidebar open by default? It's not exactly a hugely complex screen with space at an absolute premium.

We discussed this several times before, the idea is to keep the UI as simple as possible for the majority of users only interested in running a single instance. But as this issue has been confusing people in the past several times (see #388, #422, #429, #484, #523) we should finally improve this. There ideas for this discussed in the open cases #445 (comment) and #399 (comment)

Beside improvements to documentation, esp. on upgrades, my proposal for the App's behaviour would be:

• On first run(*) create a new server-entry with latest version if either
  • no server / data directory is existing at all
  • no server exists with the latest version (not sure about this one - alternatively the next)
  • all configured servers require binaries that are not provided by the installed package
• On each start of the application create a new server-entry with latest version if
  • no server is existing at all (existing behaviour)
• On each start of the application, automatically open the sidebar if either
  • multiple servers are already configured (existing behaviour)
  • the only configured server is not initialised and the installed package has multiple binary versions available
  • the only configured server requires binaries that are not provided by the installed package

(*): we currently can only detect the first run in total, not per release, IIRC. At this, potentially existing data dirs are scanned and server-entries for them created.

Does this sound useful or is it to complicated? The simpler proposal from #399 (comment) I would read as:

• Always start with expanded sidebar
• On each start create a server with latest version if no such exists

To me this defeats the concept of an expandable sidebar in general and may annoy people intentionally running an older version.

I think you need to start tracking and surfacing the versions in the UI, without falling into the slippery slope of upgrading users' data for them, which I think is too difficult and error prone.

I made a very quick mockup.

Some thoughts unrelated to the mockup:
I think the closed drawer pattern is too "old-school" and most apps start with a sidebar launch with it open by default (from the top of my head- Slack, VSCode, Garageband, Whatsapp), following web UI trends. If there's only one server it's just empty space.
There's the risk of confusion between creative a server and creating a database though.

One other problem is that the error message "The binaries for the PostgreSQL server were not found" is too generic and cryptic.

Maybe you need to show somewhere what are the capabilities of the installed Postgres.app, now that you have different flavors (12, 12+11+10, etc.). I feel it's a big source of confusion.