Hi Mans,
Starting with a spreadsheet - data in colums, no headers - put a blank column inbetween each, starting at the beginning and, in the top cell, add little snippets like this...
{ "text": "
so that, as a whole, a single line of the spreadsheet reads as a valid json entry, with a comma at the end, and 'fill' down the sheet, so it looks like this...

Then copy and paste the columns into a friendly text editor (not a word-processor). When I do it I get some kind of 'tab' character that I need to globally remove (search and replace all). I've highlighted it in the top left of this screenshot.

Then I add opening and closing square brackets and save it as .json

Drag it into TW and it appears like a regular import.

NB: if there's anything wrong with your json, you get a big red warning but nothing breaks - but use a backup, obviously.
Regards,
Richard