Celeste Studio
Celeste Studio is an editor specifically built for editing TAS files efficently. While you can use other text editors to edit TAS files, it's not the recommended methods.
Studio should automatically be installed / updated once you've launched Celeste with the CelesteTAS mod once. It'll be located in the CelesteStudio directory inside your Celeste install.
Note
This wiki is still under construction and won't have everything documented. If you'd like to help out, all contributions are welcome.
Celeste TAS