So please don't ask when this will be done. Sims 4 uses a different scripting language and generally has a whole different scripting setup, plus the morphs work differently and so far no one knows how to add a slider or if it's possible.

Please read!!! I don't know when, if ever, these will be morphable with a script. The Rules: Do not redistribute without permission. The penis mesh is the same one I used for Sims 3, originally supplied by Rockerduck. (Nipple shape ONLY.) Optionally it will show the nude body when you remove clothes in CAS and show the nude female top and the nude female and male bottoms as wearable clothing in CAS. This mod optionally will give your Sims 4 male sims teen through elder their missing equipment, and give females 3D nipples. You MUST have the June 2016 patch to use this set of mods! If you play in offline mode you'll have to go online and update - otherwise use the old Sims 4 Penis, Sims 4 Nipple mod, and Sims 4 Nude in CAS mods. The Sims 4: Anatomy Mod! Penis, 3D nipples, and optional Nude in CAS

Sims 4 penis mesh