Fielded and/or having a ratio other than 1 projects form an exception when displaying the options.
Indeed, when you create a fielded project, three new buttons (B, 1 and 2) appear in the horizontal bar :
* Button B enables display of both fields simultaneously when playing an animation or video.
* Button 1 will display the field which you have defined as the first field.
* Button 2 will display the second field of the current image.
Note that moving to the next image in a project containing fields will have the effect that the cursor of the current image does not move to the next image but to the next field (as an image is composed of two fields).
This does not modify the current project: only its aspect in the project window will be different.