Is there a way to compile a plain text file into a tsi file?
Ah, yes. Now I see it. It's a normal XML, but with some weird <Entry stuff that contains a long as Value string.
That is a bummer.
You could take a look at how cmdr decodes that. https://github.com/cmdr-editor/cmdr
Might be base64?
Is a .tsi file not plain text?
Well, it is, but it's not readable. I'm looking for a way to edit mappings in a text editor...