does anyone know how to format data entry in the way that is shown in the picture? How to add this block which is marked with red square? I can't find anywhere this option in the page designer in Oracle APEX.
Not sure if I understand your question, but if you create a "Text Field" and under its properties, Appearance > Template, select "Optional Floating". When you're done, click on Appearance>Icon then pick an item, you'll get an item which look like the first and the third in your screenshot. To get the second, change the Template to "Required Floating"