such as ctrl+shift+r in eclispe.

This is a feature that some people were asking about last year. I'm fairly sure latest PhpED doesn't do quite the same thing, but there are alternative methods that may work for you.

The first is that you can select the site name in the Workspace, then start typing the filename and PhpED will find the first matching file. Not so useful if you have lots of files with the same name.

You can also use the toolbar search box at the top of the Workspace panel. Type in your file name with optional wildcards, etc. choose find options by clicking the dropdown and then click the button to find. This method then works similar to the above one, but is a little more flexible and you can keep clicking the button to find the next occurrence. Note: Find in Expanded being ticked means only already expanded folders in the workspace will be searched, so untick that if you want to search the whole workspace.

Finally, an alternative method for finding files with a similar name is to right-click the site name in Workspace and choose Search In files but rather than searching for text, blank the text and search for a filename. Then all matching files will be listed for convenient double-clicking to open them.