While cellos, violins, etc. don't technically have frets, the notes are of course in the same layout as instruments that do have frets, so this same method works.

(It's funny how different instruments live in their own worlds. Once I showed a movable scale fingering diagram for guitar to a cello player and they had no idea what I was talking about, even though the cello has the same kind of patterns, as would any parallel-stringed instrument. Another cello player did know about scale patterns but called them "universal fingerings".)

As someone who also used to overthink memorizing the fretboard: this is a bad idea. You should strive to just plainly memorize the names of all of the notes, the relevant scale and arpeggio patterns, etc, without any kind of tricks or "system" (no, not CAGED either). This is the only path to real fluency; imagine having a neat system of remembering what each English word means and having to go through it every time you wanted to speak!