If you use the default Sims 3 setting by EA, you are limited to a specific number of sliders you can use in your game.
You can still have more in your game, for instance to mix using sliders when you create a simmeh, or when you download a sim which uses more sliders (in order for this sim to work).
With the aWT slider hack Mod, you can use as many sliders in your game as you want and all sliders will work / will keep on working. You can download the aWT slider hack mod here.
I would recommend to download the version with "Slider Range Multiplier 2x" AND "Version Default". If you use the NRaas Mod too, you should download the "Version NumSliders".
Make sure you install this Mod in the (new) correct folder path:
...\My Documents\Electronic Arts\The Sims 3\Mods\Packages\
Also make sure you have a recent resource.cfg file in the folder path:
...\My Documents\Electronic Arts\The Sims 3\Mods\
(a recent resource.cfg file is included in a PeggyZone download file for instance)
I think that should about cover it.
If you have more or further question, or I forgot something to include, please let me know
I hope this helps !!
Groetjes, Cheers, Gruessen,