Taming the GIMP with KDE window-specific settings
KDE's window-specific settings feature gives you a fine level of control over the way windows behave. It lets you change settings such as minimum/maximum size, position, overlay, and transparency. The GIMP uses multiple windows to select tools, tool options, and other items used in the process of image editing. By changing the default behavior of the various windows used by GIMP with KDE's window-specific settings, you can improve the GIMP interface.
Before getting into window-specific settings, you can use the GIMP's own window features to preserve your favorite layout. Open the GIMP, preferably in its own desktop window. Position the toolbar where it is out of the way and resize it to your preference. Open up any other dialogs you use and position and resize them too. Here, I have placed the toolbar on the left side and resized it to take up less space, and opened the Tool Options, Layers, and Brushes dialogs and placed them on the right side of the screen.
After everything is set up to your liking, go to the GIMP main window and click File -> Preferences -> Window Management. Uncheck "Save window positions on exit" and click Save Window Positions Now. From now on, each time the GIMP opens, the current position of the open windows will be restored.