Thank you for your feedback. We will definitely add tool tips. Zoom is on our road map in next releases. Regarding tech stack, the core is: electron, nestjs, sharedb, mongodb, angular, codemirror, aws and docker.
For online collaboration we use a modified version of sharedb (https://github.com/share/sharedb). Its using the operational transformation algorithm (https://en.m.wikipedia.org/wiki/Operational_transformation).