I have a system called the "Q & C System", where Q (quatrain) and C (couplet) are used as the main units and + is used for almost anything additional. When using this approach, a lack of rhyme is simply indicated by a different type or no specification of any rhyme.
3Q1C1 (three type one quatrains and a type one couplet)
If for some reason the final couplet didn't rhyme, you indicate it as a different type - a couplet that doesn't rhyme:
3Q1C2 (three type one quatrains and a type two couplet)
(A type two quatrain with an additional line whose rhyme matches the first rhyme.)
If for some reason the final line didn't rhyme, to represent that you simply omit a specification of what the rhyme is:
No specification indicates no rhyme.
Last edited by Kevin Rainbow; 03-24-2021 at 10:12 PM.