So I've found the issues I've reduce the space between "zero" and "back" and now is appear
M2_BUTTON(el_num_zero, "f4", "zero", fn_clean_dev);
M2_BUTTON(el_dev_ok, NULL, "ok", dev_ok_button);
M2_ROOT(el_num_goto_top, "f4", "back", &top_el_expandable_menu);
so I'll let you know about the next steps
thanks
gnux