Looking at Metallica's page on here - is it really necessary to list EVERY single Live show they release? They've been "officially" releasing each show through Nugs for years.

I know you can sort the page by only main releases and such, but it does take away from the shows that were proper, authentic planned releases.

Yes. Every one of them is an official release via Blackened Recordings, and is an official live album; a number of them are even given physical releases. So yes, they are covered even if it does admittedly make the discography section unwieldy.

Is there any possibility some special function could be made as an exception for Metallica's page? I'd assume they're one of the most popular pages on the site, and it'd be frustrating for viewers to scroll through if they don't realize the main/lives/demos function. Maybe some kind of dropdown like "Live Metallica series releases (2004-present)"? Or even a dropdown per year?

I've literally just looked at Metallica's page, it's been a while...what a fuckin joke. I'm not sure what can be done about this but something sure does need to be done. Sure they're official live "albums" but let's face it Metallica are just out-bootlegging the bootleggers.
But it's not just live releases, there's other pointless entries like shitty multi band promos etc that are starting to creep in and clog up band pages.
Discogs is having the same problems with these live "albums" obviously and one other band that comes immediately to mind is Pearl Jam.