A transform action can be applied on a batch of files from the Project view's contextual menu without having to open the files:
Apply Transformation
Scenario - Applies the transformation scenario associated to each of the
selected files. If the currently processed file does not have an associated transformation
scenario then a warning is displayed in the Warnings view.xsl:message output information is collected and displayed in the Results View. All entries in the Results View point to the location of the code that triggered them.