This comment says the Live Variables plugin outputs HTML (that’s not clear to me from a Quick Look at the plugin’s description): Show / Display / Embed the note properties within the note body - #15 by DandyLyons.
If dynamic solutions are acceptable (where the data lives only in properties but a code makes it render in the body too), the feature request that that comment is replying to may be of interest: Show / Display / Embed the note properties within the note body.
A plugin implementation of that approach is Meta-Bind plugin’s “view fields”: View Fields | Meta Bind Docs.
A simpler version but probably less useful because it requires a separate Markdown editor is iA Writer’s way of referencing metadata in the body: Metadata – iA.