"multi select lookup" is not selectable using sheet2app.zoho.com excel import

"multi select lookup" is not selectable using sheet2app.zoho.com excel import

I am testing out the new (for me at least) sheet2app.zoho.com excel import which looks quite nice. I have some demo data and can set a lookup relationship between my sheets of data in excel, but "multi select lookup" isn't an option for the relationship. I'm not sure I have my data structured correctly for what the import is expecting, but if anyone can layout what the generic format is that import tool needs for one to many relationships (and/or confirm that the multi select lookup should be usable thru sheet2app.zoho.com) I'd appreciate it.

Brady