Ignoring pre-selected existing nodes

For common completion frameworks (e.g. ivy, vertico), <enter> is used to select candidates.

For vertico, your case requires M-<return> (vertico-exit-input).

For ivy, it is C-M-j (ivy-immediate-done).

Reference List

1. https://emacs.stackexchange.com/questions/70436/create-new-org-roam-node-ignoring-pre-selected-existing-nodes