Initially when the accounts are newly created. The accounts will be in the 'Uncollapse' state where all the information will be displayed for the user to populate.

Once the accounts are completed please click on 'Check Accounts & Generate IXBRL Files'. This will then automatically collapse any empty data cells.

To manually uncollapse or collapse any empty data cells. Click on the collapse button in the toolbar which is located under 'Template'.

To collapse a note to the account or note to the financial statement you will need to right click the note header then go to Note Options, then mark note collapsible

 You can then choose the specific note you would like to collapse as per the below screenshot

To collapse specific accounting policies, please right click on the notes to the accounts page > notes options > Accounting Policies > Hide Accounting Policies. 

This will then display a drop down list where you can select which accounting policy you would like to hide.