The File associations branch of Settings allows you to set options for OS integration based on file type.
Clicking on the System File Associations button opens the Windows Control Panel interface for setting file associations by file type. In previous versions, file associations could be set within the application, but with changes introduced in Windows 8, Microsoft began discouraging application publishers from allowing users to set file associations inside of their applications.
If this option is selected, an "UltraEdit" or "UEStudio" option is added to the Windows Explorer context (right-click) menu, allowing you to open either files or folders in the application directly from Windows Explorer. The ampersand (&) designates that the character immediately following it will be used as the keyboard shortcut for the context menu item.
You can right click on a file (or multiple files) in Windows Explorer and select UltraEdit / UEStudio from the context menu to open the selected file(s) for editing. If Open from Explorer also opens file list is selected under Settings » File handling » Advanced, the last used workspace (and all associated files) are reloaded along with the selected file(s).
You can right-click on a folder and select "Open folder in UltraEdit / UEStudio" from the context menu. If you open a folder, the following will occur: