[JimmXinu]

Originally Posted by Amalthia

I have a Yes/No custom column for unread/read stories. Is it possible to automatically update this column when I download new stories into Calibre?

FFDL can add new/updated stories to a 'To Read' list in the Reading List plugin. That plugin can update a custom column. I use that because then I can also add it to 'Send to Devices' lists that are configured to automatically update my devices when I connect them.

You can also set it directly from FFDL by adding a static custom_columns_settings line:

custom_columns_settings:
  "True"=>#read

If you want to apply it to all sites, but also want to control other columns separate per site, use this:

[defaults]
add_to_custom_columns_settings:
  "True"=>#read

Originally Posted by Amalthia

I also have a custom columns for Warnings at A03, using the "Comma separated text, like tags, shown in the tag browser" option.

Some authors are using the option "Author Chose Not To Use Archive Warnings," is it possible to have these not added to the Warnings custom column?

Yep:

[archiveofourown.org]
exclude_metadata_pre:
 warnings==Author Chose Not To Use Archive Warnings