I present you a tool for generating different Json files - blockstates, block and item models, recipes, advancements, loot tables.
This application requires JavaFX, so it's easiest to run it with Java version 8.
Extract contents of the archive to a dedicated folder, and modify the included script to point to Java 8 installation, then use it to launch the generator.
The interface might be inconvenient, so if you need help, ask here or in my discord - https://discord.gg/sVMe8Jw.
Updated the generator with new options, and for formats of Minecraft 1.15+.