Is there a term for when a line of poetry has the words in an unusual/less natural order to fit into a rhyming structure?
e.g. Your journey will end with the ending day, You never again will pass this way;
The second line would more commonly be phrased "You will never again pass this way"
I think this is an example of the literary device known as inversion. There is a pretty comprehensive explanation of it here: https://literarydevices.com/inversion/
From that website:
As a literary device, inversion refers to the reversal of the syntactically correct order of subjects, verbs, and objects in a sentence.
and
It is also more common to find inversion in poetry than in prose because there the unnaturalness of inversion lends itself well to creating a poetic lilt. Poets might also choose to use inversion in order to create a rhyme or uphold a meter that would not work with the syntactically correct order of words.
And just a note about your last sentence: I think the second line actually would more commonly be phrased "You will never pass this way again." (At least that's how Seals and Crofts would sing it.)
poetic license
n.
The liberty taken by an artist or a writer in deviating from conventional form or fact to achieve a desired effect.
American Heritage Dictionary
That looks like ”Yoda Grammar”.
Quoting https://www.quickanddirtytips.com/articles/yoda-grammar/
[…] Carson also notes that although Yoda shifts around sentence elements, he doesn’t do so randomly. He tends to use object-subject-verb word order,* as in “Princess Leia, Han Solo digs,” […]
https://justpublishingadvice.com/star-wars-grammar-by-yoda/ provide this fun graphic.

You could also say Yoda-esque or Yoda-speak. Or sounds like Yoda from Star Wars, etc.
