JabRef 5.2--2020-09-02--5c9edc9
Linux 4.9.0-13-amd64 amd64
Java 14.0.2

• Mandatory: I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

In the window "Search for unlinked local files", after scanning the directory, a click on "Collapse all" does not collapse the tree. But this button can be used to expand the tree.

Steps to reproduce the behavior:

1. Lookup -> Search for unlinked local files
2. scan directory
3. click on "Collapse all". Nothing happens.
4. collapse the tree manually by clicking on the triangle at the root.
5. click on "Collapse all". The tree is expanded.

The "Collapse all" button works the same way as the "Expand all" button.