How to change hash checksum of a text file without changing the contents in the file I have created a text file called test.txt and the content of the file is Hello World
I would like to change the SHA checksum hash without modifying the contents and filename. Is there any way to do that without using any third party tool on the internet.
Hash functions are deterministic, same input same output. Without a modification, you cannot change the result.

The hash of a file is used at least for the integrity check. If you were able to change it without modification the integrity check will have problems.

Note: as mentioned by Ella Rose in the comments if a keyed-hash message authentication code HMAC is used then changing the key will result in a different hash-based message authentication code.