Kdenlive is refactoring its timeline to be based on Qt's data models and a QML view. This work is not yet finalized so any help there is appreciated by the developers.

There is a board tracking the current blockers for a first release with this new timeline: https://phabricator.kde.org/T7128

The work is not limited to the items on this board though: there is space for working on optimizations of both the model and the timeline itself as well as finishing the implementation of things like effects, transitions, etc.