µDock User Guide
Empty Item Menu
This menu appears when you right-click the empty space in the panel.
Add an Item. Lets you select items to add to the panel.
Add url. It can be, for example, a web address in the format https: //website.address
Add text clipping. Add text that you can later paste into any document.

All this three types of items can be added by drag and drop to the main panel.