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

JabRef version 4.2+ on Fedora 27

Steps to reproduce:

1. Add a custom export filter https://github.com/alick/jabref-export/tree/master/listrefs with the name 'test'
2. Export a selected bib entry
3. In the save file dialog, look for the custom filter entry in the popdown filter list.
4. There are two 'HTML list file (*.html)' entries in the popdown list. Neither gives the custom result. No entry for 'test'.

Notes:

• I think I might have filename clash with shipped filter. But after I changed my custom one to a new name, the result is still the same.
• With JabRef 4.1, the 'test' filter appears in the popdown list, but with a wrong suffix (DEFAULT) although it is .html in the 'Manage custom export' dialog.