I have a webform with an existing contact, which is normally prefilled but can be changed with autoselect, then up to 5 new contacts. The existing contact can then enter up to 5 new contacts. By the way, the existing contact is a person who is nominating children for Christmas presents! It all works well, however I'd like the existing contact name that's selected to be stored in the new contact records, in a custom field (so we can quickly see who added the record). I've not found a way to do this, so have tried to default it from the token [current-user:civicrm-contact]. This doesn't work, and also saw this from 2016 but that didn't work. Any ideas on how to fix this, or any alternative methods? Civi is at 5.28.3 and of course it's Drupal 7.
"I'd like the existing contact name that's selected to be stored in the new contact records, in a custom field" ->
Quick solution and better from a data point of view -> use Relationships.
That way you can not only see who has nominated a child for a present but also get a list of all kids nominated by a certain contact.