how to add transparent text and shapes to a movie? I have read this post on how to add text to a movie.

Folowing the tuto I succeded to also add some rectangular plane below the text, all on my movie in the VSE.

But, my question is : how to alow the text or the shape to be transparent over the movie ? I would like my plane shape to be something like 30% alpha. Alghough I did the setting in the 3D vue, the shape appears no transparent in the VSE.

The tuto gave some settings that seem to avoir transparency.

Thanks for help.
Blender VSE strips have a parameter called Opacity.  It is the 4th line in the N-panel for me.  If you set that on your overlays (and make sure the Blend mode is set to something sane like Alpha Over instead of Replace) it probably will accomplish what you want.