Group View: Toogle union/intersection

Using 5.*
What does union/intersection view in the Group View mean? I don’t see a difference.

When you select multiple groups, then union shows entries matched by one of them, while in intersection mode only entries matched by both groups are displayed.

I just tried it a minute ago, and for me the button does nothing. It always shows “intersection”, irrespective of being in “intersection” or “union” mode.

I forgot to mention that this is using JabRef 5.0.0-dev–2019-11-08----e7045c7a4, which is relatively recent.

I have just made the same observation as @schniepp using JabRef 5.0–2020-03-06–2e6f433: after selecting two groups with no common entries, clicking the button union/intersection does not change the display in the maintable (it only changes the union/intersection icon). Specifically, no entries are displayed in the maintable, suggesting that JabRef stays in intersection mode. My understanding is that, in union mode, all entries of the 2 groups should be displayed, right?

Is it supposed to depend on the group property named “hierarchical context”?
It this a bug or am I missing something?

@tobiasdiez: comments welcome!

This issue is possibly connected to the following problem:

(see also comments: https://github.com/JabRef/jabref/issues/4237#issuecomment-407893100 and https://github.com/JabRef/jabref/issues/4237#issuecomment-433863717)

It doesn’t work for me as well