how to List/Display All used macros/plugins under confluence

You're going to struggle.  Addon usage simply can't be done - many addons provide functions rather than content and you can't search for that.

Macro usage can be done, sort of.  There's nothing built in that will list your addons, but have a look at https://answers.atlassian.com/questions/155280 - @Davin Studer has a really neat solution (be warned it can be a little slow to render on large confluence instances, but it will get there, so give it a bit of time)