An admin responded in a semi-similar thread and suggested getting in touch with the mod to offer to join the mod-team or transfer the community: https://lemmy.world/comment/923510
My guess, given that this mod is semi-active, is that admins would want to see:
- Community members offer to join the mod-team or take-over that are ignored or rebuffed for some extended time period like a week or more. There's a bunch of unanswered at-mentions in this post, so that's a decent start.
- Evidence that the mod guidelines at https://lemmy.world/post/424735 aren't being followed (which based on this thread I think the "enough mods" guideline isn't... plus there are no sidebar rules, so I think there's a case here).
- Gather links to any posts/comment-threads that are suffering due to undermoderation, especially if instance rules at https://mastodon.world/about (yes, that's a mastodon link, the admin teams are the same and that's where they post them) are being broken and not handled.
- If the mod takes any retaliatory action like harassing you in DMs or banning people participating in discussions like this from the community, definitely document that as well.
- Crosspost this to https://lemmy.world/c/moderators with all the evidence above asking for an admin intervention.
If there's a decent paper trail of the mod not meeting mod guidelines, not enforcing instance rules, and not accepting help... I think that's the point at which they might possibly consider intervening more directly. For a semi-active mod, they probably want folks to make a concerted attempt to work it out one-on-one first.