How does the soundwizard working?

To add sounds to the global rack, use the wizard on a global instrument (it's available there too). You can not edit the global rack from an arrangement's instrument inspector.

That's the instrument inspector of the arrangement. The label "Global Rack" means a sound of the global rack was assigned. The red color indicates it was not found. Clicking on the wizard button here will not jump you to the global rack (I see how this could be confusing).

If you want to add new sounds (plugins, devices) to the global rack, go to the global rack (Playback >> Audio & MIDI Setup, or the toolbox icon). Go to the "Global Instrunents" tab and use the wizard button on each instrument you want to assign a (new) sound.

If you want to select an existing sound for instruments in the arrangement, choose so on the first wizard page there.

There are (local)racks for a arrangement for one time use and there are (global)racks for a arrangement for many time use 

Yes, that's the point.

Global instruments are used for palette surfing, progression preview, scale playback, metronome, etc. They have a fixed role, but their sounds can be changed.

The global rack provides the sounds for these instruments. And for any arrangement that wants to use global sounds as a shared resource to save load times and/or memory.

To be honest, I don't understand what you are trying to do. If you want to build a global rack, open the global audio settings. Setting up a global rack has nothing to do with an arrangement. The rack will still be there, after you closed the arrangement.

If you want to use a sound from the global rack, use the wizard and select "Browse all available sounds". The browser will show you all global rack sounds (plus the local arrangement sound) to choose from.

I think janamdo is saying that he wants to use the wizard to add a new instrument to the global rack. A far as I can tell, the wizard can only add an arrangement rack module but not a global one, so you still have to add a global rack module manually. Apologies if I've misunderstood but I've only recently started using the wizard.

The wizard is for setting up a single instrument, not for setting up a rack. It offers the convenience to add sounds and devices on-the-fly, while you configure the instrument, without the need to vist a rack.

If you want to setup a rack, visit the "Sounds" tab and add your modules, plugins and devices as needed. This is a completely differrent task not related to instruments.

If you add an instrument to your arrangement and feel it should use a shared, global sound, you'll need to add that sound to the global rack first. I understand this is an extra hoop to jump through, if that's what you mean.

I strongly doubt it's a good idea, if an arrangemement was able to modify a global rack randomly at will. What if multiple arrangements did this? How do you make sure it's the correct global rack that is being modified and not the cool rack you set up yesterday for another project? The user should be in control and decide which global rack to edit, what to add to it, how to name it and where to save it. All this should not be a side-effect of adding an instrument to some arrangement.

That's why Synfire requires you to visit the global rack editor, if you want to modify it.

Think of the global rack as sort of a master arrangement that is always open.

Building a global rack demands a bit of plannung and thought, because it often hosts larger sound libraries and includes a master and effects bus. You would rather not build that on-the-fly on an "instrument by instrument as needed" basis. That's why there is no "put on global rack" option for the wizard. It's easier to do such work on the "Sounds" tab.