Koreez Games has released the first version of the Phaser 3 Particle Editor. It's a comprehensive web based UI for tweaking the Phaser 3 particle system to your hears content. You can import images, set all of the various particle and emitter properties and then export the end-results as a json file.
It's fully open-source, so if you like what you see and use the app, please get involved to help with development.