Hello everyone,
We have published a beta version of atlassian-connect-express package with typescript type declarations. You can try it out by updating your atlassian-connect-express dependency version to 6.2.3-1. The types can be found in types/index.d.ts of the source and although not entirely complete, they cover most ACE features.
We hope you find these useful. Interested to hear any thoughts, comments or feedback!