Using Autodesk Fusion 360 for modeling

Hi. Select the item you want to modify in the viewport or the outliner ( called s4studio_mesh_1 ), File - Export - Wavefront ( .obj ), in the export settings check Selection only.

That being said, you will still have to use Blender to rig ( animation ), vertex paint ( morphing ), create a uv_1 map ( morphing ), assign type and cut number ( import ). The obj format does not retain this information.
If my memory serves me well, .fbx does not retain vertex paint and cut numbers.
Without cut numbers and type s4s will not recognize and import 3d models in the package.
.blend is the only available format that stores all information needed for the item to function properly, so you will have to use it as a bridge anyway.

I explained how to export the headpiece only, without the body.
Autodesk fusion 360 is not a commonly used software in the sims community. This is the first mention of it on the forum, so it is unlikely that anyone in Creator help knows anything about it to offer some insight. Here's what google has to say about it . If this won't help, you will have more luck on that forum.

You can export as OBJ from Blender to Fusion (assuming Fusion can open OBJ files? I'd think it can - I only have experience with older versions of Autodesk 3D Max which could use OBJ files, but I'd think Autodesk tends to have OBJ support for most of their programs since it's such a basic file format, and I doubt they've had any reason to remove it). You're going to need Blender to export from and import back to S4Studio, so you're going to have to import into Blender from Fusion at some point anyway. 

If you want the program to be compatible without Blender, you're going to need plugins that for Fusion and for S4S, which is no easy task (there's probably a very good reason why program plugins are in limited supply, because there's a limited number of people in the community who knows how to make them). 


Back in the days when I had access to 3D Max I was only modding for TS2, and found Milkshape a mess to mesh in - but meshing in 3D Max and importing the finished mesh as an OBJ file and doing the last finishing touches on the mesh worked like a charm (I did a lot of accessories which involved linking up to a rig, which involved Milkshape since there were no plugins for Max). I'd imagine you'd want to do pretty much the same, but using Blender as the "bridge" program between S4Studio and Fusion, so you are going to need to learn how to do do the "bridging", such as linking the mesh to the rig.  

Nowadays I've kind of started getting used to Blender, and while it is more difficult to use it does have a lot of the tools I need, so it's not the worst program. A lot of strange shortcuts to learn, though... 

Do you have any experience using Autodesk Fusion? Have you looked up tutorials on how to modify imported meshes? Looked up problemsolving sites for Autodesk? Googled if there is an answer? 

My first go-to tends to be Google if I have a particular meshing problem in for instance Blender. That, or finding a Youtube tutorial of some sort. Same if I'm having problems in pretty much any other program and need an answer quick. You're a lot more likely to find answers searching around that way. 

It's probably a bit unlikely that you'll find someone who can help you around here. You're likely to find answers for Blender, but less likely to find answers for a program you and probably very few others use. 

Anyway, I did try to Google: "autodesk fusion 360 locked imported object" and found a few results, but I only skimmed over them, so you'll probably want to search around a bit. The forums.autodesk.com/ site could be helpful, though. 
forums.autodesk.com/t5/fusion-360-design-validate/problem-moving-imported-object/td-p/7870792
forums.autodesk.com/t5/fusion-360-design-validate/how-do-i-scale-an-imported-object-component/td-p/7130563

I see plenty of people asking questions about Blender, I see no reason I can't ask questions about fusion 360, on the off chance someone here knows how to deal with it re: obj meshes exported from sims4studio.

It's far more likely people here would know the process from exporting from S4S to blender to Autodesk to Blender to S4S than people on an autodesk forum would. 

Pretty much nobody here uses Fusion 360, but everyone has to use Blender because it is directly tied to S4Studio (you can't make a single mesh without it, unless you're willing to go the route of TSRW or S4PE, and there you're somewhat tied to programs like Milkshape or anything that uses OBJs or similar). So that's why people are asking about Blender here.

One of the best places to ask for help about an Autodesk program would be on the Autodesk help forum, where there are people who do use the program you're asking for help with. Chances are you probably won't find anyone here who can help you. Personally I've barely even heard of the program, and I haven't even opened an Autodesk program the past 3 or so years, so all the help I can offer is via Google searches (which you can probably do a bit more successfully yourself since you can test and see if what you find works on your file).