add documentation for mutli-preset export

Author: zisoft

content/module-reference/utility-modules/shared/export.md

@@ -96,9 +96,12 @@ style
 mode
 : When applying a style during export this option defines whether the history stack items of that style replace the original history stack of the image or are appended to it. Technically speaking, in append mode history stack items of the style will constitute separate instances of the respective modules on top of any existing ones (see also [multiple instances](../../../darkroom/processing-modules/multiple-instances.md)). As a consequence the original history stack will remain in effect with the new items being applied in addition. This way you can apply an overall adjustment (e.g. exposure) to a number of exported images while respecting the settings of each individual image.
 
-export
+start export
 : Press this button to start a background job to export all selected images. A bar at the bottom of the left hand panel displays the progress of the export job. Furthermore a notification message pops up reporting the completion of each individual export. You may click on the pop-up to make it disappear. You may abort the export job by clicking on the "x" icon located close to the progress bar. 
 
+multi-preset export
+: This section allows to easily export the selected images with several different presets in a single export run. Select the desired presets and press the "start export" button. Make sure that the presets specify individual settings for filename and path so that the exported images do not overwrite each other.
+
 ---
 
 **Note:** Images that are selected but currently hidden (because they are members of a collapsed group) will not be exported.