The XpressDox Explorer does not contain an explicit “Search” function.  Nonetheless, you can search in the currently open folder for a file, using the Windows file system’s wild card syntax.

The example below demonstrates how the wild card string *letter*.xdtpl will list all (and only) XpressDox templates with the string “letter” in the file name (type the wild card string in the File name area and then press the Open button)
XpressDox Explorer