SEVERAL solutions exist:

Use a “Select Values” step renaming a field while selecting also the original one. The result will be that the original field will be duplicated to another name.

It will look as FOLLOWS:

This will DUPLICATE fieldA to fieldB and fieldC.

Use a calculator step and use e.g. The NLV(A,B) operation as follows:

This will have the same effect as the first solution: 3 fields in the output which are copies of each other: fieldA, fieldB, and fieldC.

Use a JavaScript step to copy the field:

This will have the same effect as the previous solutions: 3 fields in the output which are copies of each other: fieldA, fieldB, and fieldC.

Several solutions exist:

Use a “Select Values” step renaming a field while selecting also the original one. The result will be that the original field will be duplicated to another name.

It will look as follows:

This will duplicate fieldA to fieldB and fieldC.

Use a calculator step and use e.g. The NLV(A,B) operation as follows:

This will have the same effect as the first solution: 3 fields in the output which are copies of each other: fieldA, fieldB, and fieldC.

Use a JavaScript step to copy the field:

This will have the same effect as the previous solutions: 3 fields in the output which are copies of each other: fieldA, fieldB, and fieldC.