Toggling this option either allows you to move any sub-element anywhere you want in a record (without that sub-element being constrained by property/sub-property constraints) or it locks sub-elements to their parent elements.
To invoke this option, either:
This will either:
If no check mark appears to the left of this option (default), then you cannot move a sub-element from under the parent element to which it belongs.
If this option is checked, then you can move a sub-element from under a parent element, and place it under a different parent element. This is not technically correct, but is sometimes necessary, in order to make the elements export in the correct ISBD order for a MARC record. Click on the option
For example, to line up the example below, correctly:
245 10 $a Shaolin Dancing Warriors / $c Isabel Muänoz = Shao lin wu shi / Yishabeier Muniaosi.
This option works on a record-by-record basis–it is always 'off', by default (locking sub-elements to their parents); so you will have to turn this 'on' (unlocking sub-elements from their parents) for each record, as needed.