I also love draw.io (now diagrams.net). Additionally it can be self-hosted if needed and it has a well built API for integration with other systems. Login is n

I also love draw.io (now diagrams.net). Additionally it can be self-hosted if needed and it has a well built API for integration with other systems. Login is not required by the way, You can choose "Device" or "Decide Later" when presented the save options.