Guessing you probably figured this out since it was like a year since you posted, but if anyone else was looking for an answer on this, there's some extensive documentation on the Import/Export tool in the Mike Urban Model Manager manual, Section 7. The Import/Export tool should almost be thought of as a GUI-based scripting tool; the SWMM preset is just one of the presets built into the tool (as mentioned on Page 136).
If you haven't tried the Advanced mode, you may have some more luck, as it's a little clearer what's going on in my estimation (you'll have to select Show Details after entering the Advanced dialog). Similar presets from the Wizard can be seen in the Advanced mode so you can see exactly which fields in Mike Urban are matched to which fields in SWMM. If you double click on one of the presets (e.g., [i]Export SWMM[/i]), a bunch of table mappings will be expanded to show how everything is mapped.
There is some limited logging for the Import/Export tool in %USERPROFILE%\AppData\Local\DHI\2016\MIKE URBAN\all-utf8.log
(if stuff goes wrong with the import due to something like an illegal character in a MUID, it may show up in there)