Clean-up Genre's of Existing Metadata

[snuffomega]

I'm lost down a rabbit hole and I'm hoping someone can pull me out!!! My goal, which I thought would be doable, has evaded me for which seems like an eternity. ANY help would be GREATLY appreciated. If there is a suggested workflow and/or SOP I should be following, let me know as well. I'd like to make the process sustainable and as simplified as possible (I was attempting to upload and edit the existing metadata within my files, but I am just hitting my head against a brick wall)... Anyway, thanks in advance:

Goals no.1 & no.2 are the ideal priority, no.3 is a distant memory....

Goal no.1 - Simplify / Standardize Genre's:

• Alternative Rock > Alt. Rock
• Rap / Hip-Hop > Hip-Hop
• etc.

Goal no.2 - Add a Genre based on existing genres:

• If the genre has anything with metal (metalcore, black metal, etc.), add 'Metal' if it doesn't already exist
• If the genre has 'Reggae' and 'Rock', add "Reggae-Rock" if it doesn't already exist
• etc.

Goal no.3 - Add a Genre manually to the existing Genre string;

• buy either selecting the folders or creating a temporary library to add this GENRE to them. This is more for how I personally generalize a specific group of artists that may or may not be accurate, but is correct for ME and how I view them (if that makes sense).

For no.1 - I tried variations of a few different plugins. The closest (yet so far away) was with lastgenre trying to format:

lastgenre:
   auto: no
   source: album
   Canonical:
     Alternative Rock': Alt. Rock`
     Abstract Hip Hop': Abstract Hip-Hop

For no.2 - I was tying to make it work with inline, but obviously made no progress there either:
inline:

   - add_metal: |
     if item.genre and 'metal' in item.genre.lower() and 'Metal' not in item.genre:
       item.genre = item.genre + ', Metal'

Any ideas, suggestions, and/or config fixes would be greatly appreciated!!!