To undo and redo operations

In the ribbon menu the Undo / Redo is part of the Workbench toolbar (above the home tab).

Alternatively use the keyboard shortcuts:

• Ctrl+Z to undo
• Ctrl+Y to redo

Note: When you delete objects by emptying the Recycle bin (accessed by right clicking on the Recycle bin and selecting Empty Recycle bin), this is a permanent operation which can't be reversed using the Undo command.