'Table transformation Google Sheets

I'm trying to convert such table:

into such table:

First table is very big, and is being changed automatically by another user.

I'd like to use Google Sheets' query function. Any idea how?

Thanks in advance!

Solution 1:^[1]

use:

=INDEX(QUERY(SPLIT(FLATTEN(B1:D1&"×"&A2:A&"×"&B2:D), "×"), 
 "where Col2 is not null"))

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Solution	Source
Solution 1	player0