In addition to XLSX utilities @saqimtiaz pointed out, you can also use the JSON Mangler plugin, I have a dedicated TiddlyWiki for both that acts as a data preparation wiki then drag and drop to the target wiki.
It is also possible to export as CSV file, then paste that into a tiddler and write your own parsing, but XLSX and JSON Mangler save a lot of fuss. They are good investment of your time if you do a lot of data interchange.
XLSX imports them as desired in to tiddlers, JSON Mangler packages the tiddler into a single plugin tiddler.