Renaming submenu “parent slug” option to null is the solution to this.
add_submenu_page(
null,
null,
null,
"manage_options",
"edit-testimonial",
"edit_testimonial"
);
Renaming submenu “parent slug” option to null is the solution to this.
add_submenu_page(
null,
null,
null,
"manage_options",
"edit-testimonial",
"edit_testimonial"
);