WPS Office not showing in "Select Application" default app window

In Ubuntu 18.10 I am trying to enable WPS Office apps (Writer, Spreadsheets, Presentation) to open Microsoft Office files as default.

After right clicking on the file (e.g. a .docx) > Open With Other Application, the Select Application window appears having LibreOffice Writer as default.

However, after clicking on View All Applications, WPS Office apps are nowhere to be found in the list.

The same issue exists with right clicking on the file > Properties > Open With tab.

How could I make WPS Office apps appear in the list with compatible apps for Microsoft Word/Excel/PowePoint files?

Know someone who can answer? Share a link to this question via email, Twitter, or Facebook.