You're looking to create a feature for the MCL Mangai Tamil font keyboard layout in TTF (TrueType Font) format.
He unpacked the archive. mcl_mangai.ttf. And beside it, a scanned image: keyboard_layout.pdf. mcl mangai tamil font keyboard layout ttf
The MCL Mangai font is a popular non-Unicode (legacy) Tamil TrueType font (.ttf) often used in publishing and design. Because it is a non-Unicode font, typing with it requires a specific keyboard map where English keys are "remapped" to Tamil characters. Keyboard Layout and Mapping You're looking to create a feature for the
Example:
k + e + d → கெ + ் → கெ? No — careful: type k → க, then e → கெ, then d → கெ்? That’s wrong.
Actually: Online tools: Search for "MCL Mangai to Unicode