How to edit .msi file?

Please tell me how to add/change registry values in the .MSI installer file using NSIS ?

NSIS does not use MSI files so you are asking in the wrong place. You can edit a .msi with the Orca tool found in the free Windows SDK.

Many users use NSIS to work with MSI files.

For example, to get information about different msi parameters, as well as to edit tables. It is

much faster than working with orca, etc.

There are a few tools for this:

https://nsis.sourceforge.io/MSI_Functions

I really need to add-change registry data in the msi file table.

Please help - how to do this using API functions ?

That code you linked to just provides information about already installed MSIs.

NSIS is simply not the right tool for whatever you are trying to do, try asking here or here instead.