When I want to overweight levels in our CBC design programs, I start by replicating the levels in the attribute entry interface that I want to overweight (the software won't accept duplicate labels as different levels, so you make replicates have at least one character difference in the labels). I generate the design. Then, I export the design to .CSV file from the Design Tab + Export.
Then, I modify the .CSV file to recode the duplicated levels back to be the original levels.
I then modify the project (the attribute list) to delete the extra labels, so I'm back to my original attribute level lists in the CBC software. I then use Design + Import to import the modified .CSV file.
I then retest my design to check the frequencies and efficiency of the design.