Are you trying to save the character with the penis as a complete figure that you can load later? If so it's pretty easy to do, but selecting 'character preset' as the save type is only going to save the base figure without any attachments like genitalia, hair, clothing or whatever. What you want to do is select the save type as 'scene subset'. Here's how to do that.
Once you have your character created with all grafts, hair, and whatever else you want to be a part of it, open the folder in your content tab where you want it to go. Click on the '+' sign at the bottom of the tab. This will open up a popup that has the different save types available, I'll assume this is where you've been going to save as a character preset, so hopefully you're still with me. Near the top of the save types you will see 'scene subset'. Click on that. It will give you a new popup box that has everything in your scene with checkmarks next to them. You want to deselect everything that is not your character, such as any cameras, lights, or props that you may have loaded. Leave only the checkmark next to your character. Before you click save, make sure that everything that is part of your character is properly parented to them, or else it will not load when you try to add them to a new scene. When you open a new scene in Studio, go to the folder where you saved your character and double click it like you would to load anything else, and it will be loaded just as you saved it, pose, hair, pecker, and all.
You can even do this with multiple characters like couples or more, but I've found that the best way to do that is to parent all of the characters to the first one you loaded once you've posed them how you like, this insures that they load in the right positions. I also use this feature to save complete scenes like interiors, environments, or whatever, so that I can load them all later with one click. Character preset is only useful if you're just saving the base figure with no attachments, and I never use it.