Combining diacritical underdot not working for me

I have recently transitioned to Mac and am learning what is important to know about shortcuts in text editors. It works for me to use the Unicode Hexinput keyboard, and when I hold the option key and type 0305, a bar appears over the letters. Similarly, I would assume I could make a dot under a character, i.e., by holding the option key and typing 0323. But it doesn't work for me. I appreciate any help with this. I would appreciate not to use the equation option or the emoji box, as it will be much faster for me for my work, if I am able to type these codes.