Transpose multiple text-based columns to single column while retaining record ids

Hello,

I am new to this service. I am hoping someone can help me with an issue I have been struggling with.

Attached is a sample dataset. Columns D through AG need to be arranged as individual records, but columns A through C need to follow each record as each row (as currently organized) is an event. I have tried all kinds of functions (transpose, index, match, offset, etc.), but this appears to be over my head.

Can someone help, please?

Thanks in advance!