Older versions had a "Remove unused references" button next to their list. It might causing missing problems for some references but I was fine with it.

In newer versions this button is not available here. However in this link, Microsoft said that you can still doing it. The problem is this right click menu item is not available for me. I cannot see it. Not right clicking on "Solution" neither on "My Project" settings nor "References" tab.

What I tried is just Ctrl + R, G to removing unused Namespaces in the code.
My project is still heavy in term of output size since I enabled "Copy to path" property of used references.