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.