The first column holds the proto-language. Originally, I just arranged it by extant language, but this makes it unclear whether (say) a Sanskrit change describes the fate of a sound in PIE or Proto-Indo-Iranian.

The second column holds the target language.

The third column holds the sound in the proto-language that underwent a change.

The fourth column holds the resulting sound.

The fifth column contains the environment.

The sixth column is used for citations.

You can use a seventh column for notes.