You can use pattern checker to automatically replace the URL with the original one.

"bsky": {
    "regex": "https?:\/\/go.bsky.app\/redirect\\?u=(https?.*?)",
    "replacement": "$1",
    "decode": "true",
    "enabled": "true",
    "automatic": "true"
  }

(it’s possible they will add more parameters in future, in which case you may want to restrict the selection to not be essentially anything after u=)

I don’t know if it is just one site I use or simply a limitation, but I have found that custom fields don’t seem to work on mobile.