Changing object/path filling's opacity without changing the stroke's opacity

Question

I would like to reduce the opacity of the filling colour of an object/path and keep the stroke of such object/path unchanged.

Is there a way of impeding this relationship so I can only reduce the opacity of one?

Answer 1

Color selector has alpha slider. In the next image both circles have black stroke and cyan fill. The rightmost circle has 50% transparent fill color (alpha=128)

Unfortunately there's a thing you maybe didn't expect. The stroke is half-way covered by the fill and the covered half become visible.

A fast workaround is to have 2 separate shapes (=edge & the fill) or to make a white stroke + grey fill copy on the top and use it as opacity mask. An example:

The opacity mask is set by selecting both layered objects and applying Object > Mask > Set

The 2 shape approach needs the stroke as a filled area which has a hole. It can be made easily by subtracting the fill area from the stroke which is converted to path. I do not recommend it because exactly fitting seam has 1 pixel wide transparent zone which needs a narrow stroke to be covered => more complex that the opacity mask version and not easily editable.

Answer 2

change the alpha value in the Fill submenu on the Fill and Stroke tab.