You may modify county borders. Simply click on the “Edit Borders” button in the map toolbar and start moving the markers around.
When you’re done, click on the same button again to validate your changes. The realm borders will be automatically recalculated.
Please note that in order for the realm borders to be correctly drawn, the space between the markers has to be small. If the markers are too spaced out, you might experience some problems with the realm borders.