This highlight below is the only evidence that there’s a glass door in this opening:
In most other camera angles, the glass is 100% invisible.
And this is despite me setting a grey tint on it (I don’t want frosted, but even if I do tweak that, all that happens is that the highlight fades away).
Hello - there is not a good way that I know of. I recommend making two glass materials, one tinted, maybe with low gloss and not quite transparent. Use the tinted one for rendered display, the clear one for rendering. It is relatively easy to select all objects using a particular material from the material panel context menu for the material and assigning a different material is similar.
If it is reflection that is lacking, then (also judging from your metal image, but I can’t really see what is going on there) you may want to ‘RestoreDefaults’ in the Rendering panel.
What happens if you put some stuff on the other side of the door (I mean so as not to have just white space) ? Is the glass material a Rhino default one?
To assign materials to a block, BlockEdit and assign to the objects in the block or ByParent so it will use the layer material.
If I put things behind, it’s still pretty much invisible save for the highlight. If I color it bright green, I can see a faint, faint shade of extremely light green where the door is.
The most important thing for glass is having an en environment to reflect(or pretend to reflect in the case of the OpenGL view.) What are you using for that?