Custom element doesn't exist anno 2021

Please don’t kill me if I should’ve found this info somewhere…
I can’t understand why I’m getting a custom element doesn’t exist.
All solutions I can find is about adding resources in yaml-files but today you can only add it in Lovelace UI - resources.
Therefore I can’t find the solution for this.

I have added as resources:
/config/www/pollenkoll-card.js
/hacsfiles/lovelace-card-tools/card-tools.js

When creating a new card with the code
type: ‘custom:pollenkoll-card’
I get an error:
Custom elements doesn’t exist: pollenkoll-card

Hopefully someone can point this noobie in the right direction…

Try

/local/pollenkoll-card.js