Kdenlive effect properties section disappeared

I was working, editing my videos and a section of Kdenlive has disappeared. When I apply an effect on a clip a section should show up in the middle of the window where I can manage the effect. For Example if I apply the effect "fade to black" I'm able to select time and duration for this effect.

The scratch on the image is ugly but useful, the section should be in this position.

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This subwindow is called “Properties” and can be enabled in the menu bar via ViewProperties:

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From version 20.12.0.2 on the subwindow is called “Effect/Composition Stack” instead:

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