If you want to use the filestore in your own actions, use the following interface of the \Workflow\VTEntity class, given to the action in $context.
To store a file inside the filestore:
$context->addTempFile($filepath, $filestoreid, $filename);Parameter
| $filepath | String | The temporarily path to the file you create This file will be moved to the central tmp directory inside Workflow Designer | 
| $filestoreid | String | The ID you want to use, to store the File | 
| $filename | String | The filename of this file. Could be used by tasks to use the correct filename | 
To load a file from filestore:
$file = $context->getTempFiles($filestoreid);Parameter
| $filestoreid | string | The ID of the file you want to get | 
Returns
array(
   "path" => <absolute path to the file>,
   "name" => <filename you set during addTempFile>
) 
					