With KeePassXC you would do this by adding new entries for each alias and then reference the username and password values of the "base" entry. I believe the feature still isn't in a release, and the UX isn't there at the moment.
The problem is that they can't deviate from the official KeePass database format, so adding something like aliases requires hacks like the above.
The problem is that they can't deviate from the official KeePass database format, so adding something like aliases requires hacks like the above.