I have DirectoryOpus 10 pinned to the taskbar. When I right click the Opus icon the first item under "Tasks" is "SearchLayout" which opens a search window. Is there any way to create a button which will perform this task?

Open the Preferences dialog to Layouts and Styles / Layouts.
While that dialog is open, select the Customize command from the Settings menu in a Lister.
Then you can drag & drop a layout from the page in Preferences to your toolbars.

Thanks. This works great.

Looking at the code for the button shows this:
Prefs LAYOUT="SearchLayout"

Is there any way to have the search window open so that it defaults to starting the search in the current directory of the lister from which the window is spawned?

Yes, change the command to:

Go CURRENT LAYOUT="SearchLayout"