I came across a weird problem. I have created multiple field groups, then after I finished displaying them in PHP, I came back to look for a field slug and the field box was no longer in the edit panel. I checked and unchecked “Fields” checkbox, relaunched all my setup multiple times, however the “Fields” box is not displaying. Maybe someone has had a similar problem and managed to solve it? I don’t think that there could be my mistake in PHP file, because it was only a few get_field(”) lines.