Thanks to the impressive work on the holistic system, you've collected one of the best databases that recognizes relative chords for known songs. But even with https://www.hooktheory.com/trends there's no way to filter to songs that use only certain progressions.
So, you have created select examples in https://www.hooktheory.com/theorytab/difficulties and elsewhere but no way for anyone to query the database for other ones you didn't make.
For example, in my own collecting of notes during my teaching, I've marked things like this:
- songs that use only I & IV
- songs that use only I & V (and the following progressions)
- I V
- I I V I (several nursery rhyme songs)
- I … V | V… I | (period w/ first phrase half cadence, second stays on V), so:
- Singin' In The Rain ♥ #pent
- though usually with jazzy embellishments 6's, 7's, 9's, filler chords…
- Jambalaya On The Bayou — Hank Williams
- Apples & Bananas (Ooples oon Boonoonoos)
- Polly-Wolly Doodle
- You Never Can Tell — Chuck Berry
- Waltz Across Texas — Ernie Tubbs
- Pistol Packin’ Mama
- Tulsa Time — Don Williams
- Achy Breaky Heart — Billy Ray Cyrus
- Okie From Muskogee — Merle Haggard (ugh)
- The Bottle Let Me Down — Merle Haggard
- Cocaine Blues — Johnny Cash
- 25 Minutes To Go — Shel Silverstein (recorded by Johnny Cash)
- Hang Down Your Head, Tom Dooley
- Deep In The Heart Of Texas
- Iko Iko
- Shoo Fly
- Down in the Valley
- Mein Hut
- Animal Fair
- Hush, Little Baby
- Where Oh Where Has My Little Dog Gone?
- Marianne (Caribbean folk song)
- Pay Me My Money Down (Caribbean folk song)
- I Kona — George Kelepolo
and on and on… through more complex progressions. Your database allows searching for songs that contain some order of chords, but not that contain only a certain order or that use a certain phrase structure.
I'm not sure if I can even search (maybe through the API?) for something like the list of songs that use only I, ii, and IV (and not V).
The database could be queried in all sorts of useful ways if you would release the database more publicly, ideally under a free license like https://opendatacommons.org/licenses/odbl/