The Clip Window is a floating/dockable window that displays clips. You can drag and drop text onto the Clip Window and drag text from the Clip Window onto your files.

Clips are Clipboard-like files. In fact, the Clipboard is considered a clip in Source Insight. You can create a clip anytime by using the Copy to Clip command, the New Clip command, or by dragging and dropping text onto the Clip window. A clip is really just a file buffer that you can select and edit normally. The only difference is that the Clip Window (and associated commands, like Paste From Clip) makes it easy to cut, copy, and paste between your source files and clip files. Also, clips are automatically saved when you exit Source Insight.
You can toggle the Clip Window on and off by running the Clip Window command, or by running the Activate Clip Window command, which makes it visible and then sets the focus on the Clip Window edit field.
Clips are automatically saved to the Clips subdirectory of your Source Insight directory. Any text file that you place in that Clips subdirectory will be automatically loaded when Source Insight starts up.
You can also drag a file from Explorer onto the Clip Window to open a file as a clip.