Redstring uses "models" to generate strings. In the bottom pane, list each model on its own line. Wherever you want Redstring to substitute from a column (top panel), use the column's label.
In this example, let's say the first column contains the following list...
Bob
Fred
Jim
The second column contains the following list...
Jane
Mary
Elsie
The model...
{A} likes {B} and {B} likes {A}.
...will substitute each name from the first column in place of each {A}, and will substitute each name from the second column in place of each {B}.
When we're happy with our columns and models, we click Compile. It will finish within moments, and then we can click "View Results". We will see the following output...
Bob likes Jane and Jane likes Bob.
Fred likes Jane and Jane likes Fred.
Jim likes Jane and Jane likes Jim.
Bob likes Mary and Mary likes Bob.
Fred likes Mary and Mary likes Fred.
Jim likes Mary and Mary likes Jim.
Bob likes Elsie and Elsie likes Bob.
Fred likes Elsie and Elsie likes Fred.
Jim likes Elsie and Elsie likes Jim.
However, if we wanted more variety (and some sentences that indicate unrequieted love), we should copy the contents of the first column to the third column. Then, we change our models to...
{A} likes {B} and {B} likes {C}.
After compiling, we get...
Bob likes Jane and Jane likes Bob.
Fred likes Jane and Jane likes Bob.
Jim likes Jane and Jane likes Bob.
Bob likes Mary and Mary likes Bob.
Fred likes Mary and Mary likes Bob.
Jim likes Mary and Mary likes Bob.
Bob likes Elsie and Elsie likes Bob.
Fred likes Elsie and Elsie likes Bob.
Jim likes Elsie and Elsie likes Bob.
Bob likes Jane and Jane likes Fred.
Fred likes Jane and Jane likes Fred.
Jim likes Jane and Jane likes Fred.
Bob likes Mary and Mary likes Fred.
Fred likes Mary and Mary likes Fred.
Jim likes Mary and Mary likes Fred.
Bob likes Elsie and Elsie likes Fred.
Fred likes Elsie and Elsie likes Fred.
Jim likes Elsie and Elsie likes Fred.
Bob likes Jane and Jane likes Jim.
Fred likes Jane and Jane likes Jim.
Jim likes Jane and Jane likes Jim.
Bob likes Mary and Mary likes Jim.
Fred likes Mary and Mary likes Jim.
Jim likes Mary and Mary likes Jim.
Bob likes Elsie and Elsie likes Jim.
Fred likes Elsie and Elsie likes Jim.
Jim likes Elsie and Elsie likes Jim.