Archive:Kdenlive/Manual/Effects/Custom
Effects - Custom
The Custom Group in the Effects List is where Effects appear when you choose Save Effect from an Effect in the effect stack.
Defect
There might be a defect in 0.9.2 of Kdenlive where saving a new Effect makes the existing custom effect invisible in the Custom section. With the upshot that you can only have one custom effect visible.
Work-around: Start and Stop Kdenlive. The restarting Kdnelive causes the Custom effects to be updated and you can see all the ones you have saved.
See this Bug Tracker Entry