Stat > DOE > Modify Design
After creating a factorial design and storing it in the worksheet, you can use Modify Design to make the following modifications:
By default, Minitab will replace the current design with the modified design.
Modification
Modify factors: Choose to rename factors or change factor levels, and then click <Specify>.
Replicate design: Choose to add up to ten replicates, and then click <Specify>.
Randomize design: Choose to randomize the design, and then click <Specify>.
Put modified design in a new worksheet: Check to have Minitab place the modified design in a new worksheet rather than overwriting the current worksheet.