Following applies to version 5.x of UAE with only AS1/2 support (dated 2007), and does not contain any information about improvements in later versions. (Somewhat more recent information can be found in UAE 2010 pre-release notes and UAE 2011 release post)
You can open a SWF file by using File|Open command or dragging it to the URL Action Editors main window. You can also open a projector file or any file that has an embedded SWF. In this case UAE will search the file and display Select SWF Dialog if more than one SWF candidates in the file is found where you can select which one to open.
If there are errors while opening the SWF you’ll be presented with the Error Log dialog. These errors might be trivial or not. In this case, you should definitely test the output more than usual.
After the file is loaded you’ll see the location and actions of all the URL-related actions in the list in the URL Actions Tab. You can see the extra actions (all actions that include ‘=’, ‘==’, ‘===’ and ‘eq’ operators) by using the toolbar button or Options|Show Extra Actions menu command. Selecting each item will also display the location in the Preview Window. (If the Preview Window is not open, you can open it by pressing F5).
You can preview the SWF with any modifications you have made by pressing CTRL+Enter.
You can disable the selected item by using ‘Disable’ button. You can edit the selected action by double clicking on it.
While editing the action, a list of available strings will be presented. Simply select the Url string and double click to edit it. Original action is always visible at the top for your reference. (This version of URL Action Editor does not let you write expressions. You’ll only be able to edit strings in it). Clicking Close immediately changes the action.
You can view and edit movies properties using the Movie Information Dialog.
If you need to change any symbol, you can do it either in the Library Tab or the Timelines Tab. The difference is that changing a symbol in the library will affect all instances of that symbol, while the timelines tab allows to change a particular instance. Again, Preview Window will let you easily locate the symbol you’re looking for.
You can edit initial text of an editable text symbol, import URL of an imported symbol or Import/Export ID of a symbol in the Library Tab. You can also Edit Colors of graphic and text symbols.
In the Timelines Tab you have the option to add a getURL action or a new layer to any frame. You can also hide a layer or edit the instance name of a symbol.
You can edit the location of a symbol using the Edit Location… command:
You can save the new SWF by using File|Save As command. There’s no Save command for your safety but you can select the original SWF in the Save As dialog and replace the original.
If the SWF is changed, URL Action Editor will warn you when closing or opening a new SWF.