what do you have in mind on using in the template file.
you can use any page as template, but it won’t evaluate the lua functions inside them. if you have functions in the template, this simple approach will only get’s the template as string and no functions. to use functions or REAL Template files it’s more complicated to implement.
here is a simple approach to get the contents of the template as string from an external page
local template = space.readPage("Library/Custom/NewJournalEntry")
event.listen {
name = "editor:pageCreating",
run = function(e) if not e.data.name:startsWith("Journal/") then return end
return { text = template , perm = "rw" } end
}