The three Navigation tabs can be minimized either by double-clicking on the tab header or using Minimize Tab in the tab's right-click menu. Clicking on a minimized tab brings it back to its regular place and size again.
All other tabs can be maximized by double-clicking on the tab header or using Maximize Tab in the tab's right-click menu. When you maximize a tab, the Navigation tabs are minimized to make as much room as possible available and the tab you maximized fills all available space. Double-clicking on the the tab again restores all tabs back to their original size. The latter can also be accomplished by deselecting the Maximize Tab right-click item.
An icon in the main status bar indicates when a tab is maximized. An alternative for restoring the original size of all tabs is to double-click on this icon.