Under the "emm_config" section, change the value of the DisplayFilingOptions parameter by adding 16 to the existing value.
Figure: DisplayFilingOptions paramenter
This is a bitwise operator. If, for example, the value is 7 to indicate that all three options are enabled, change it to 23 (add 16 to the existing value). This ensures all three default filing options are available/visible on the EMM task pane, and the check box for the Custom25 field is also displayed.
See the following figure with the Custom25 check box (in red).