I like to use PromptLayer for this. But you could easily set up a simple CRUD web app to track prompts/average completion token # length, different variations.
I want to have folders with different personalities. And I should be able to start a new conversation in that folder, with that personality. Think instead of one global system prompt, you will have multiple system prompts.
There is also awesome-chatgpt-prompts (https://github.com/f/awesome-chatgpt-prompts) which has some interesting ones. What are you looking for?