I want to store 100x100 grid cells in a VTK file.
Along with the cells and points, I want to store 2 scalar values,
X = 100
Y = 100,
which represent the X and Y dimensions of the grid

The above values can not be stored as point_data or cell_data as X and Y are properties of the whole grid.

https://examples.vtk.org/site/Cxx/PolyData/FieldData/
The above link mentions that "For data that does not align with either points or cells, FieldData should be used"
The Mesh class has a field_data attribute

But the vtk_sections list present in _vtk_51.py does not have any section related to field data.

So what is the best way to store this?

As a workaround, I tried adding a FIELD_DATA section in the _vtk_51.py and made some changes to the write() and _read_section() methods.
This approach solves my issue, but I am not sure if this is valid from the domain point of view.