There is no setting in the provided information that allows changing or extending a time limit for typing an address in the To line in Outlook on the web or Outlook.com. The available controls for the To, Cc, and Bcc fields relate to suggestions and address handling, not to a typing timeout.
If the To field is losing focus or closing too quickly, the behavior cannot be adjusted via a documented Outlook setting in this context. A practical workaround is to type the full address in the message body or in a separate editor, then copy and paste it into the To field.
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