The phrase "be to" is often used to indicate an event or action that is scheduled to happen in the future. In such cases, synonyms for "be to" include "will", "shall", "is scheduled to", "is planned to", "is slated to", "is expected to", and "is intended to". However, depending on the context, "be to" can also mean "to be obligated to" or "to be supposed to". In such cases, alternatives for the phrase include "must", "have to", "should", "ought to", and "need to". Using varied synonyms for "be to" can help to add diversity to the language and make the writing more engaging.