[arch-general] [OT] Settings problem: Why is Thunderbird so silly?

Hi all, I want to select an application for opening an attachment with an alternative editor (a PDF file with LibreOffice Draw in this case). When I want to select the application, I get the list of last opened files (i.e. text files, which obviously are not able to run ...). Trying to search for "sdraw" presents me with a waiting cursor ... waiting endlessly. I'd guess I have to set some options somewhere, but I don't know which - or do I even have to edit some XUL file? I doubt, that Thunderbird is really so "silly" just not being able to find some application. BTW, my desktop is XFCE, latest firefox (latest system update today). Kind regards Peter