[JimmXinu]

Originally Posted by JimmXinu

Short answer: The genre(w/add_genre_when_multi_category) -> crosscat -> category trick isn't going to work with AO3 and a few other sites; those that don't internally collect category.

After some more thought, it occurred to me that while adding crosscat to category won't work, adding it to fandoms will:

[archiveofourown.org]
include_in_fandoms:fandoms,crosscat

Full INI code:

Spoiler:

[defaults]
is_adult:true

## Add "Crossover" to genre
add_genre_when_multi_category:Crossover

## a tmp var, basically.  
## Need to add to your add_to_extra_valid_entries line.
add_to_extra_valid_entries:,crosscat

## fill with genre skipping replace/include/exclude
include_in_crosscat:genre.NOREPL

## only include Crossover in crosscat.  
## Again, incorporate with your existing, if  you have one.
add_to_include_metadata_pre:
 crosscat==Crossover
 description==asdf
 characters==asdf

## remove Crossover from genre.  
## Again, incorporate with your existing, yada yada yada.
add_to_exclude_metadata_post:
 genre==Crossover

include_in_category:category,crosscat

[archiveofourown.org]
include_in_fandoms:fandoms,crosscat

So effectively the same thing.