Adding and removing associations between mimetypes and applications is done with the following syntax in the mimeapps.list file:
[Added Associations] mimetype1=foo1.desktop;foo2.desktop;foo3.desktop mimetype2=foo4.desktop [Removed Associations] mimetype1=foo5.desktop
The [Added Associations] group defines additional associations of applications with mimetypes, as if the .desktop file was listing this mimetype in the first place.
The entries in [Default Applications] should also be considered to add an association between application and mimetype in the same manner.
The [Removed Associations] group removes associations of applications with mimetypes, as if the .desktop file was NOT listing this mimetype in the first place.