I’m simultaneously working with three programs and moving info into DTPro. But when I click on one of the other programs, DT minimizes (OSX 10.8x). Is there a DT setting to keep it from minimizing or some OSX setting that I need to change?
But while the DEVONthink application is frontmost you can open the Groups & Tags panel (Tools > Show Groups & Tags (there’s a keyboard shortcut). This is a floating panel, so that it can be available from other applications to allow drag & drop of data to any location in any open database.
Remember also that you can drag & drop data onto the DEVONthink Dock icon.
By default, DEVONthink does not automatically minimize to the dock. Is it merely on another desktop? Over here, DEVONthink does not minimize when it and other apps are in the same desktop unless I press option-command-H, the OS X shortcut for Hide Others (other apps). If however, DEVONthink is on a different desktop, switching to another app may cause DEVONthink to not be visible. Check Mission Control in Apple help for the many options available for working with desktops and how to move apps together onto the same desktop.
If you have an iPad on the same network as your OS X machine, I’d suggest looking into Splashtop Streamer – when Streamer is running and Spashtop’s companion app is running on your iPad you can use the iPad as a second monitor. When I’m doing work like you described, consolidating lots of data into DEVONthink, I find it useful to put DEVONthink’s window on my iPad and drag back and forth from there to my main workspace. (I have no relationship with Splashtop, and there are other apps for this purpose – this just happens to be the one I use.)