Diacritics with macron

Hi Im writing a document including classical Greek and im having trouble finding how to get some of the diacritics with macron. Most accented charshave their own unicode but macron with accent etc requires combined diacritics. Ive found out how to get acute / grave accent with macron by combining macron character with u+0x301 / u+0x300 respectively but i cant locate unicode to combine breathings with macron, or combined  breathing and accent with macron. Can anyone help me out? Im using lo 6.0.7.3 with ubuntu 18.04.8.ThanksGary