Alright I spent about an hour on this so here's a guide for how to customize the girl's traits:
Make sure to follow the guide exactly and do not add or remove anything else.
There are additional values in the saves, I'm not sure what they do, so I haven't experimented with them, didn't see a need to.
Without further ado, the guide:
Step 1. Open the game, generate a girl, and add her to the Album. That's the heart icon under the pink demon on the left side bar.
Step 2. Navigate to the following location in your file exlorer:
C:\Users\<Yourcomputerusernamehere>\AppData\LocalLow\KitOlmek\My Jazzy Lolly Crush\saves
Step 3. If you followed step 1 and only have one girl saved in the album, you will find a single file with the extension .myjlc. It will look like this: save-250326-225941333.myjlc
Format is "save-yearmonthday-hourminutesecondmilisecond". 25 is year, 03 is month, 26 is day, 22 is hour, 59 is minute, 41 is seconds, 333 is miliseconds. Credit to Markisd for figuring out the last group of numbers.
Step 4. Open the file with a text editing software. I strongly recommened Notepad++ for any save game editing in any game where it can be done in a text editing software.
It will look like this:
Step 5. Close the game, else it may save over your changes.
Step 6. Changing the things you want:
Step 6a. Name:
Using the example I posted above, replace "Sumiko" with "Whateveryouwant". The result will be:
"name":"Whateveryouwant"
Step 6b. Traits:
Using the example I posted above, the girl has:
"_traitRefs":["anal-a1-virgin","mood-distracted","pain-sm3-exp","touch-clit+","lolly1","anal-","vaginal-"]
This is where the trait information is stored. Each trait must be in quotation marks ( " " ), and traits must be separated by a comma (,). Do not add any spaces anywhere and make sure there is not a comma after the final trait.
Here is where you can add or remove any traits you wish. You can experiment as you wish, but I believe contradictory traits may either not load or crash the game or cause any other kind of behavior.
I've made a list of all the traits below (If there is one I missed after an hour of refreshing, let me know, preferably with an attached save so I can add it to the list):