FUSE customization slider doesn't work.

this is correct, its just a case of putting 100... actually you can imput upto 999 but 100 is best for human characters

p.s, Fuse will keep working until you allow Adobe cloud to update itself

Sorry to step in, @John Waller . First rule should be that Adobe shouldn't buy competitors and then kill their products without providing a decent alternative. As a designer, I would really appreciate that THEIR tools stop to define MY craft! The fact is that now there is NO comparable alternative within the CC suite and that sucks! Sorry for the little burst.

That said, @xee5CBB  asked a simple question. The tool, for what I have seen, seemingly works (there is no error showing up, the app opens and you are even capable of creating (and exporting) a character), but the customization of the features seems "deactivated" (which, I assume has been done intentionally). So the answer should be:

1. Sorry, Adobe has discarded that feature (and therefore, maybe they could "grey" it, or simply remove it, for the matter...)

2. It seems you are missing something and here are the steps to make it work: (...)

So, dear @xee5CBB , it seems that Adobe does not provide a robust alternative. If like me, you pay sth like USD 1K a year (!!!) to Adobe, you will soon discover that you actually end up working with other software than the ones provided in the CC suite, because the Adobe products are less and less innovative and performant (Adobe, feel free to contact me, I have concrete examples, if you are interested). For instance, to create photorealistic renderings in 3D, I now use Blender (sorry Dimension), which by the way can also very handily replace After Effects (and its attempts to sell you Cinema4D for a prohibitive price)  in a lot of circumstances, Marvelous Designer / Clo3D for cloth making (sorry Substance) and now am frantically looking for an alternative to Fuse because for once I needed a tool to create realistic mannequins/rigs for my 3D projects... and it doesn't work anymore (thanks Adobe! And do not suggest your lame Mixamo vamp up, it's pathetic compared to the features Fuse used to offer!). At this stage, seemingly out of options, I am about to try MakeHuman. Fingers crossed.

And while I am sure Adobe people work very hard, we may not head to the same direction anymore. The last bits that keep me working with Adobe are Photoshop, Illustrator and Premiere Pro (to a lesser extent After Effects... but mostly because I didn't know how to to certain things in Blender at the time). Knowing that Affinity could potentially replace the first 2 and Final Cut Pro is already on my computer... what can I say? "Dear Adobe, we are Creatives, not cows to milk! You are here to provide solutions for our craft, and that is (or should be) your talent! We may be way less without you. But you would be NOTHING without us!" Thanks.