If I have a visualforce page embedded on my custom object's standard page layout, should it show when I create a new record or only on edit?
I created a basic form for some questions where I needed a longer label than what the field label allows, but it's only showing on edit and not when I create a new record. I'm using lightning experience
No, Visualforce cannot be embedded in that way. (See this old IdeaExchange post, which essentially declines to implement that use case in favor of unspecified alternatives).
Instead, you'd need to override the New action with a Visualforce page or Lightning component that completely replaces the native page layout, which is a little heavyweight for many applications. You might consider instead whether a Record Create Quick Action or a Flow could help address your needs in terms of a more interactive record create experience.
