Firefox 70 added a new „Certificate Viewer“ feature which moves the „Window“-based GUI to a „Web-Page“-View.
- different look
- no new features
- missing features
- Export Certificate
So this is no „new feature“ but a „modification of an existing feature“ – with less features.
Reenable the former full featureset
about:config security.aboutcertificate.enabled := false
As part of my personal „move away from evernote“ initiative this has been documented here, maybe it’s interesting for somebody.