Sorry, for my bad english, i speak german only!
“You can specify the audio and subpicture as default when playing backup DVD by the arrow. This “Default Arrow” can be moved to other audio/subpictures by clicking just to the left of the checkbox for the item. Clicking on the arrow itself turns the default off. Selecting a default subpicture will force start the subtitles on most players.”
Although I set the arrow for a sub-title, this does not function with each film that the sub-title is indicated automatically. Sometimes it, but only, folds if I keep all sub-titles of all languages with and set then the arrow, as usual, if I liked to keep only the German sub-titles.