More than 1 CF7 value to 1 3rd party field

Have you tried just putting the same thing in “3rdparty” column? You may also need to fiddle with the “multi value separator” setting.

1. i.e you offering to create 3 different fields, but all of them content to send in one cell of the 3rd party service?
2. I see it in the plugin settings. Where can I find documentation fo this?

In the faq:

I need to submit multiple values as…
By default, if more than one value appears in the post request for the same field/key, they will be joined by the ‘separator’ value like &post-values=a,b,c.
However, if you use [] as the separator it will instead create multiple keys like &post-values[]=a&post-values[]=b&….
Use [#] to retain the numerical index: &post-values[0]=a&post-values[1]=b&…

Although now that I think of it I might not have exposed a setting to customize the delimiter. Please check and let me know if it’s working for you.