@Gimli OK I hope I got what you want. I converted the Python code from two Stackoverflow threads (1, 2) into a small KNIME workflow. You might want to check if you could adapt that.
You would enter the data and the variables and the numeric borders
The lower part of the workflow would just use the x-axis min and max as a default. You might be able to tweak the design of the y-axis.
kn_example_python_numeric_integral.knwf (341.2 KB)