If you're using U-tab for the first time you'll notice the mouse-pointer will move to the left of the screen, exposing the variable index. That's where all the variables are listed and it collapses on the left to maximise the user's workspace. If you want to hide it again, simply move your mouse-pointer off the index.
The first time you start U-Tab an example project will be loaded and you will see a table on the screen (on very large projects, press 'F9' to calculate the first table).
Very simply, you're looking at two areas: the table construction area (Table Construction Area) and the table display area (Table Display Area). At the very top of your screen is the menu bar which contains various drop-down menus. Below the table area are the toolbar that shows short-cut icons and the information area that displays helpful information regarding any current processes of U-Tab. Don't worry about those for the moment; we're only looking at the table construction area and the table display area for now.
As with most functions in U-Tab there is a short-cut for toggling the variable index: ctrl+i. This feature can be switched off by un-checking the appropriate box on the advanced tab of the options menu.
See also: Short-cut keys