When you open the OSes open, save, save as, save as copy, and export dialogs or the custom ones from libreoffice then should retain the user's previously selected filetype. This only happens when using LO's custom dialog for save, save as, and save as copy.
I'll just set this to NEW, mmkay?
*** Bug 98151 has been marked as a duplicate of this bug. ***
We're replacing our use of the 'ux-advise' component with a keyword:
Component -> LibreOffice
Add Keyword: needsUXEval