In Kdenlive what are called transitions are actually blending methods which work pretty well also for creating video transitions.
This blending features are very well implemented and useful but in the standard professional video editor apps (where this excellent approach on layer blending we can find in Kdenlive is missing) transitions are a different thing. They are crossfades, wipes, 3D effects (as page curl, cubes, etc.) and all the way to pass from an image to another (or to cross fade two audio clips) and they works only on edit cuts.
At today on all the main video editor apps you can apply the transition effect on a single track (this is made mostly for using the keyboard) and you have a panel for fine tune the parameters.
I suggest to change the name to the current transitions in something like "Compositing and Transitions" and "Fast transitions" to the standard way to apply transitions when it will be implemented.

https://old.kdenlive.org/node/9458#trans