Thanks for your replies.I'm not exactly sure wich version of Cinelerra I use. It is Cinelerra GG - Infinity, built: 31 october 2020Inkscape is 1.0.1. ...

Thanks for your replies.I studied the problem again, and add a screenshot here. The problem starts when I drag the effect to the timeline.And whatev...

@phylsmith2004 and @andreapaz, thanks for your replies.I tried both ways (and now retried SVG via Inkscape)Even by dragging the effect to the timeline...

Thank you, Phyllis and Andrea.The 'Flip' was what I needed.I admit... I scrolled through the effects... but was a bit lazy to find to right one.