Also desperately need to export/import highlights. And UI preferences.
Luckily i've recently separated theme import/export into a standalone component, so at least we can export/import UI preferences with highlights easily :DD
Upd.: BE doesn't support mutes as of the moment — created an issue for implementing the support: pleroma#482 (closed). Import / export of mutes will likely be a separate issue / MR and depending on the above issue.