I am importing nodes with taxonomy terms for one vocabulary. I have a set of terms that I would like to use that are set up with their own columns.
I know feeds tamper can explode a set of data in one column using a delimiter and apply that to a term, but I need each taxonomy term to be in it's own column. This is easier for readability for the people who are setting up the database.
Unfortunately, I do not think this is possible at the moment.
If you map several columns to the same taxonomy term field in a Feeds importer what will happen is that the last input (furthest to the right in the input CSV, or possibly last in the order given in the mapping) will override the previous ones, and only if there is data in that input. This might be useful in some cases but does not provide the functionality you are looking for.
I think your best bet is to write a new script to implode your columns, and then use tamper to get them into the nodes.