KaleidaGraph System Requirements
Please note: KaleidaGraph is a 32-bit application and will not run under Catalina (OS 10.15). A 64-bit version is under development, but it is too early to provide a release date. If you must use OS 10.15, we suggest using a program like VMWare Fusion or Parallels/Parallels Lite to install and run an earlier version of the OS as a virtual system which would provide access to 32-bit apps. If this was an avenue you wanted to explore, here is a link to an article that has information on setting this up using Parallels Lite: https://www.imore.com/how-install-macos-vm-run-your-32-bit-apps
Other options include downgrading back to your previous OS, or if you have multiple Macs, having one run Catalina and leaving one at an earlier OS. If you have access to a Windows computer, the Windows version can open your existing Mac files.