To delete an “HD cache”/”Gel file” for a specific Action, right-click the Action and select the “delete HD cache” option inside the context-menu, as illustrated here:
You can also use one of the two options available inside the “edit” drop-down menu: See the following illustration:
The option "Delete All HD Cache Files of All graphs" deletes all the HD Caches that are inside the “Working directory for cache files” (see section 4.5.1. for more information about this parameter). If all the users on the server are using the same “Working directory for cache files” (i.e. they have the same %TEMP% MS-Windows Environment Variable), then you should avoid using the option "Delete All HD Cache Files of All graphs" because this might delete the HD Caches of the other users on the server (and they won’t like it!).