There are several functions available above the form canvas for editing your forms as you build them out.
From left to right, they are cut, copy, paste, select all, undo, redo, and delete.
The arrow above also indicates where you can see the trace stack for actions taken to undo/redo as far as you need.
To cut/copy/paste/delete, be sure to first select an item from the form or drag your finger around multiple items.
Read the form building guide for more info on creating forms.