trouble merging plans

The instructions on importing training plans says that you should be able to merge two plans (in my case a 1/2 mary and an OLY) by selecting which sports you want to import for each specific sport. But every time I try, it erases all the previously imported data from the first plan (ie. I import only S/B info from the OLY plan and it wipes out all the R workouts from the other plan and vice versa).

What am I doing wrong? Thanks!