Correct! The Random Marking Applicator gives you one random marking on chosen lion, and there is a slight chance that it could be a special marking. However, you can choose your own marking with the Marking Applicator; it's custom markings only though, and you cannot add any special markings.

It's best to design your own lion in the wardrobe with your own markings that you want! You can customize your main male at the bottom of the Oasis, but if you want a lion with a special base and/or special markings, or maybe a mutation, then you'll have to buy a separate lion, customize it, and then spend 10 Gold Beetles to make him your main male if your current one hasn't retired yet.