Instrument definitions follow a specific XML file format which I believe mirrors the scheme in the Apple OS midi system. A person can edit or create these files and put them in a folder where DP on Windows will find them on startup. (I.e. there is no button to push for importing these files.) It is not nearly as simple as Sonar's INS files. I found if I made any little mistake in XML syntax, DP would disappear from my screen. So it helps to have a text editor that helps identify XML syntax errors.
But the whole scheme offers some big payoffs in the ability to control what gets sent to the synth when changing patches, maybe even sysex or other special bank select messages. Sonar can send only certain bank select messages, so synths that need special sysex messages, such as changing from single channel to multi-channel "performance" or "combi" modes, need a sysex event programmed into the event list just ahead of the patch change event.
I have not yet looked for a patch searching GUI like Sonar's. That would be nice.