I usually import files via the DT Pro Files > Import > Files and Folders route. I’ve created a special group for receiving imports. Here’s how: Create a new group. Name it “Imports” if you wish. Now go to DT Pro Preferences and click on Imports. At the bottom of that panel you will see a scrollable button that will allow you to choose a destination group, e.g., Imports. That’s one way. (But imports using scripts will usually dump the new item(s) in you top level group, unless the script is specifically modified to offer a choice of groups or to send new items to a designated group.)
If you are a dragger and dropper by preference, here’s something you will probably love:
 Open DT Pro Preferences. Make sure that “Hide ‘Groups’ panel when inactive” is not checked.
 Select Tools > Show Groups. A new panel will be displayed. It displays all the groups in your database. Click on (or drag a file onto) a group. If there are subgroups, they will now be visible – and if they in turn contain subgroups, clicking or dragging onto them will display those subgroups, and so on.
 Size and move this panel for your convenience. Mine is on the right side of the screen, just wide enough to display the group names, and taking up the full vertical dimension of the screen. Now, grab the top of the panel and move it down to where the top is just showing at the bottom of the screen, and just above the area that triggers display of the Dock (I’ve got the Dock set to hide). It’s important that the green button be visible; when clicked, the almost hidden panel will jump back up to where you had last placed it (click the green button again, and the panel will jump back to screen bottom). Another approach would be to minimize the panel (click on the yellow button) instead of placing it near the screen bottom, and display it when needed by clicking on its icon in the Dock. Use the approach you prefer.
Now the Groups panel is available to you from any application, Carbon or Cocoa.
Here are some uses:
In the Finder, select one or more files that you wish to import. Now bring the Groups panel into view and drag the files to your chosen destination for them. Easy.
In any application, select text and/or images, pop up the Groups panel, and drag the selection to your chosen destination. This works with applications such as MS Word, which isn’t compatible with Services, or just about any application you may use. Neat!
How’s that? It’s much more versatile than dragging items onto the DT Pro Dock icon.