Vivaldi 1.14 includes improvements for several existing features: vertical reading for Reader Mode, Markdown support in Notes, rearrangeable panels, and re-orderable search engines. Several dozen bugs are also addressed in the new version. There are no new security fixes in Vivaldi 1.14.
Somewhere along the line — possibly in this release — Vivaldi’s weird bookmark editor (the one in the bookmark sidebar) was finally made usable. It’s still weird, but at least now it works in a way that makes sense.
The release notes for Vivaldi 1.14 have additional details.