If a project is not under source control, use the following method to rename it.

In a Datical project directory, modify the .project & datical.project files with the new name.
In the GUI, right-click the project, then select Delete. When asked to confirm, DO NOT select Delete project contents on disk (cannot be undone)
Move the project folder to a TEMP folder outside of the project directory and rename the folder to match the new project name
Choose File > Import to import the project from the TEMP directory

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