You can use the dm_custom_checkin_prompt configuration option to control the visibility of the content dialog box. Previously, the content dialog box opened by default during a custom checkin. Now, the default dialog box setting is controlled by Windchill preferences. Now, during a custom checkin to Windchill, you need not specify the type of contents to be checked in and this option makes it easier.
User Interface: File > Check In > Custom Check In
Click here to know more about this option