Hi, is it possible to hide an object on stage, but having it rendered nonetheless ?
 

You could set the object's display type to Outline, which is almost as good.  You can get an object to be hidden from preview but shown in renderers, but this takes editing the scene file / CR2, or possibly there's a python function to do it.

My Freebies

There are two visibility settings , one for normal render, one for raytracing.

If you turn off one and leave "visible in raytrace' on , and have raytrace set in render settings the item will render.

 Visible setting just makes it unvisible both on stage and render, "visible in raytracing" make is visible or unvisible in reflections. So this is not a solution.

I tried to set "hidden" to 1 and "visibleInRender" to 1, but the figure is still not rendered.

Oh oops, I guess that doesn't work after all.  Setting the object's display type to Outline is probably as good as it gets.

My Freebies

You can do this in the shader node(s) for the object.

In order to make the object completely transparent in the Preview, you will also need to adjust the render setting for Preview transparency. By default, Preview transparency is limited so that you can still see fully transparent objects as semi-transparent in the Preview. Change this setting to Actual and they will disappear completely.

*Edit - the reason why this works is not immediately clear. I can explain if required.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)

 Thank you very much !