The existing fields have the limits they do because discord only lets embeds have so many characters, and if the embed total is even 1 character over the limit it fails to send entirely. The embed character allowance has to be spread across the multiple possible fields and make sure that someone who’s maxed out every field can still send their member cards.

The Names & Display Names & System Tag functional hard limits are also due to Webhooks (what PK sends your messages as) having a hard limit of 80 total characters.

If you need more space for more sets of pronouns, or for most of the fields, they do support website links so you can link to a site like pronouns.cc or pronouns.page to get around the character restrictions.