When changing to Edit mode, the form content is parsed. If the form content can be successfully parsed according to the formatting rules, the information in the form content is inserted into the correct place in the Table of Contents and Form Area. Otherwise IRIS Forms stays in Source mode.
Note that the form content is not validated - it is simply parsed so that the correct 'fit' can be found for the form content in the Table of Contents and Form Area. It is then up to you to correct the form if errors are found so that it can be successfully validated.
To switch to Edit mode:
Select the Edit button in the toolbar