In theory it should be possible. But where are you expecting to see this? Sources are displayed in many places. The sources list, the sources tab on an individual page, or multiple sources attached to a single fact or event, or, …..
A screen dump would help.
Also, what should happen to sources in the same display that do not have a date? Do they come before or after dated sources? You might not have any but I’m sure someone will.
I’m about to start preparing all the support material for the next release, so it won’t be possible immediately and not in this release.
I meant by a fact of an event. See the file.
If there’s no date, I should prefer after dated sources, but maybe someone else should prefer before.
Now I have sometimes multiple sources for an event, but they are presented in order of input.