While this is an old series (2012!) and some options inside of KDenLive have changed it's still really well done, as are their other articles on KDenLive. I read through it all today after bookmarking it some time ago and still learned something.

1. Kdenlive Part 1: Introduction to Kdenlive
2. Kdenlive Part 2: Advanced Editing Technique
3. Kdenlive Part 3: Effects and Transitions
4. Kdenlive part 4: Color correction
5. Kdenlive Part 5: All About Audio
6. Kdenlive Part 6: Workflow and Conclusion

One important thing I noticed, in part 3 they are no longer called "Transitions" but "Compositions".     #>