It's excellent, just a few minor tweaks to do:

For some reason my spreadsheet did not work properly with " as the string delimiter, so I swapped it for a pipe |. I also had to insert a comma at the end of the string to generate a new column:

Thus to be able to Copy-Paste directly from a text editor to a spreadsheet I had to do the follow search-replace operations:

Search ":
Replace with :|,

Search ,"
Replace with ,|

If you prefer a different string delimiter, that's fine. I'm not sure " is optimal, since user-entered data will sometimes have " in it.

Second, Please adjust the first row to have:

ROW INDEX as first column header and DATA as second column header, and then the column index numbers, so that #1 starts on the third column.

This will now change the numbering that occurs in the Sparse Cartesian Product Coordinates (SCPC).

One other thing: It seems to me that the blue button at top left "Add a Header Value" should be "Add a Column". Do yo agree?