If I have a plugin used in a project if I open the VST manager it becomes inactive there, so I can’t change its visible/hidden status.
For example I used a plugin ABC in a project but later on removed it from my plugin list. It’s hidden. Now I want to use another instance of it. But to do that I must first add it to my plugin list. I can’t because it’s “hidden” and I can’t “unhide” it because it’s basically disabled. I have to close the project, then go to the plugin manager and activate it and add it to the list and then reopen the project.