When I add the tint effect to a clip in the timline, I can edit the timeline points in the properties widget, but there are no blue circles or lines to edit them in the timeline clip itself. Reproducible: Always
That's probably a "won't fix", at least for now : the effects coming from the frei0r repository all have "simple keyframes" that look how you describe, but there is currently no easy way AFAIK to turn this into a real keyframable effect (because the latter is more flexible in terms of what you can do, in particular you can choose a different interpolation). The best solution overall IMHO would be to implement a keyframe management similar to the one of blender for example, with a dedicated widget summarizing all the keyframes for all effects. This would help insure synchronicity for example.
Taking alcinos comment into consideration will close this until changes happen upstream or a refactoring in Kdenlive.