Suppose you have a CSV column 'SOURCE' which you want to use for several fields in Drupal. This is how this can be done.

Mappings:

SOURCE -> Temporary target 1
Blank source 1 -> field 1
Blank source 2 -> field 2

The order of the mappings is important.
You can add as much Blank source * as you want. Just make sure it starts with 'Blank source ' and all is well.

Tamper:

First, for each Blank source x -> field x use the Copy source plugin to copy from SOURCE to field x, or use the Rewrite plugin to use tokens to populate the field.

Then add tamper plugins as you wish.