Change curves alpha in preview

Hi, does anyone know if it’s possible to change curves transparency in grasshopper? Thanks.

It’s not. In general when you start drawing transparent geometry you have to sort all the shapes back to front lest they occlude each other in awkward ways. Grasshopper doesn’t even do this for transparent meshes (which is why sometimes one transparent shapes completely hides another one behind it). I think for curves this would look really weird really often.