Finally! It worked! Thanks a lot for the info!

To summarize:
Text edit the Package.appxmanifest file and change from
<Resources>
<Resource Language="x-generate" />
</Resources>
To the languages your game supports.
<Resources>
<Resource Language="en-us" />
<Resource Language="fr" />
<Resource Language="de" />
<Resource Language="nl" />
<Resource Language="pt-br" />
<Resource Language="ja" />
</Resources>
Then edit the vcxproj of your project and before the add this (using the same language codes from before) :
<AppxBundleAutoResourcePackageQualifiers>DXFeatureLevel</AppxBundleAutoResourcePackageQualifiers>
<AppxDefaultResourceQualifiers>Language=EN-US;FR;DE;JA;NL;PT-BR</AppxDefaultResourceQualifiers>
Okay, now just generate the build and send it to the store and all the languages your game supports will appear as expected. =)