JMeter __TestPlanName function reference: syntax, parameters, and practical examples for parameterizing test plans with dynamic values.
Also documented in context in the full Functions and Variables reference.
The TestPlanName function returns the name of the current test plan (can be used in Including Plans to know the name of the calling test plan).
Example:
\${__TestPlanName}will return the file name of your test plan, for example if plan is in a file named Demo.jmx, it will return โDemo.jmx