Hi, Thanks for the comment.
You can create your own pre-processor prompts for the general chatting mode. You just need to add a text file to your user data folder. You can open this folder from the config menu in general chatting.
Add whatever prompt you want to a text file and reload the program for your pre-processor prompt to work. That is one way to add your own character.
In regards to the 400 error could you provide a bit more information? I haven't come across that error at all while testing. It could also be an API Key issue.