Hello William,
The CODM enclosure (Swell) parameters are fairly basic compared to a full definition format like the Skinner. The full format allows each individual pipe to have several different aspects modified for the enclosure settings whereas the CODM has a more basic method in which you only have to specify the first and last notes of a rank to be enclosed and the first and last filter data information, then Hauptwerk scales the rest of the pipes correspondingly in between these values.
So, the means to adjust indiviedual pipes in an enclosure are not present in the CODM and this is intentional to keep the file formatting more simple for the user. You can still experiment more with the minimum and maximum frequency settings within the CODM to adjust each rank until you get an effect you are happy with. Swell simulation is a fairly difficult part of creating the virtual organs, so it may take some time to get it to where you are happy with it.