Notes need to be made specifically for Quest or PC and are not interchangeable between the two. You can tell which platform a note is for by the file extension. .bloq files are for PC while Quest uses .zip files.
The latest Custom Notes mod can be found in the #pc-mods channel in the BSMG Discord or in Mod Assistant.
Once installed, you should see a CustomNotes folder in your install folder, with some sample notes installed for you. This folder is also where you will place *.bloq files.
You can download more bloqs from ModelSaber.
Custom Notes for Quest are provided by the Qosmetics mod. The latest version can be found in the #quest-mods channel in the BSMG discord. Notes are called qbloqs and are currently hosted in the Qosmetics Community Discord.
Inside the game in the main menu you will see on the left a CUSTOM NOTES button under the Mods section. Pressing it will open up the menu you can use to select which notes you want to use.
Upload the .qbloq file to your Quest using the BMBF Web Interface. You can then select which note is active from the Qosmetics menu in-game.
Bobbie's Bloq Guide is a good resource for creating custom notes from an existing model.
Note that this guide does not cover 3D modeling the notes. For that, we recommend looking up some tutorials on Blender!