ETA: Q1/2021
Server and web settings part done:
Help with mobile, desktop apps and browser extensions highly appreciated 
On the web vault selecting default defined usernames looks like that:
I wondered about how to do it in one input, but I cannot find the solution that satisfies me.
I’ve created three PRs:
Now browser extension preview:
And a PR: Default usernames by michalchecinski · Pull Request #1645 · bitwarden/browser (github.com)
This is really a cool and needed feature.
I hope you don’t mind, to make the interface cleaner could you have pulled the usernames from the identities?
Edit: Sorry, one more thing. I’m not trying to nitpick, I do appreciate what you’re doing.
Could you also have done a datalist element instead of a drop-down menu? This way you would not need the extra dropdown and the username can be the datalist where the user can type whatever they want or hit the drop-down and pick something.
For the identities, I use my one identity, but want to have many usernames, e.g. my different emails, some usernames for where there are no mail option on login. So the way I did it, had more sense to my use case. Also, I think that identity is something different from username/login, and I don’t think that it is needed to have many identities just to have many default login options.
For the datalist element. Main reason that I haven’t used it is that Safari support’s it from somewhat high version 12.1, as it is listed here: : The HTML Data List element - HTML: HyperText Markup Language | MDN (mozilla.org). Safari 12.1 showed up in the March 25, 2019, which is rather new.
But I am not frontend dev nor macOS user.
I belive that two of those decisions must be made by PO from Bitwarden team.
Bitwarden’s latest Safari extension has moved to Safari Web Extensions, which is only available on Safari 14+ (Safari Web Extension | Bitwarden Help & Support). I believe future development will be done on this extension version.
It might be good to get Bitwarden team to comment on the support status for Safari 13 and older.
Great info. Thanks 
But as you said let’s wait for the Bitwarden team comment on that matter 
I saw that my original post was liked by Bitwarden team member @tgreer I posted this thread almost 2 months ago, and don’t want to sound rude or pushy, but I will hope that me and all users that need this feature would use it. So highly appreciate the input from you on the questions in this thread
Any updates to this feature? It would save so much time quickly using a common login username, instead of typing it out every time.
I’ve thought to myself many times in the past when typing out the same old email address that it’d be fantastic if Bitwarden could save a list of usernames for me to quickly select from. @michecinski This looks absolutely brilliant, thank you! Bringing it to mobile would be incredibly handy, too.
@tgreer Any update on when this could be implemented?
We’re in the process of a release currently. @eliykat has been reviewing open PRs, he may have an idea of when he can take a look.
Thank you for your kind words. Really appreciate it 
Yes, the feature in mobile app is also on my mind, but I’ve got really lot going on, so haven’t got time to implement it. But if anyone have time to do it, I’ll be really happy to help
Sadly I am a mere user and have no coding abilities, otherwise I’d love to help! Maybe since Michał’s already done the hard work for the web vault and extensions, the BW team could quickly put together the implementations for the mobile and desktop apps for the sake of cross-platform unity - might even make the next release perhaps
As an aside, this is what I love about open source projects like Bitwarden; it’s really cool to see the community put together new features that we’d all find useful. Cheers again @michecinski! 
If you don’t use default usernames will the forms on the interface disappear or it will add useless clutter?
For example for increased privacy I use unique usernames for each single website and I’m using unique email addresses from a catch-all domain (for example here is [email protected])
The additional form controls will dissappear
cool
i also like the idea of the datalist element. It’s true that safari 12.1 is recent, but anyone on macos > 10.13 (macs sold after the year 2009 got that update) should have safari 13.1 or higher
I can’t provide a hard timeline on progressing this PR in particular, but I’ll be sorting through community PRs over the next few weeks to at least provide some initial feedback and next steps. This PR does represent one of the more popular requests so I’ll make sure to check it out.
Agree the datalist implementation sounds like a nice near minimal UI way of doing things. I’d definitely be keen to see this feature too!
