Irrlicht Engine

What is the proper way to define and use tabs? I tried adding with gui environment, but i cant see them.

Create an IGUITabControl and have that addTab(), instead of your GUI Environment.

Check Mesh Viewer tutorial.

// create tab control and tabs
IGUITabControl* tab = env->addTabControl(
core::rect<s32>(2,20,640-452,480-7), wnd, true, true);
IGUITab* t1 = tab->addTab(L"Scale");
IGUITab* t2 = tab->addTab(L"Empty Tab");

Are they off screen? I tried to add more than would fit on the tool window in the meshviewer example. It depends on how long the name is.

Just play around with the numbers, and see what you can do. It is unfortunate we can't do more tabs like other Windows programs have... normally when they don't all fit in one line, another row beneath them can be made.