You will note that you only have the Change Item 
facility. The Add Item 
and Delete Item 
facilities are not available from this Panel. This is because when displaying a statement you are looking at only a small part of the whole account.
If an item is missing from the display, it does not necessarily mean that you have not entered that item.
It probably means that you have either ticked it off against another statement, or not ticked it off against any statement. To add the item in this Window without first checking this possibility would give you a lot of extra problems.
Similarly, if you find an item in this display that does not appear on the statement currently being checked, it would be wrong to delete the item without checking to see if it properly belonged in a different statement.
If you find an item appearing incorrectly in the display for this statement, then use the Un-Tick 
function to remove the statement number from the item. The item will now be included in the unreconciled items for this account. (It does however remain in this display until you re-display this statement.)
If you find an item appearing on the statement but not in the display, click the Details tab which will show you all the items for this account.
Next use the search facilities to try to find this item.
If you do find it, use the Change Item facility to change the statement number reference.
If you don't find it, use the Add Item facility to add this missing item.