Advanced symbols in Microsoft Word | Combining diacritical marks

I work with ancient Greek inscriptions and need access to the advanced symbols that are used in publications of this type. Specifically, I am concerned with the creation of so-called 'combining diacritics', i.e. any operation of diacritical marks using Greek fonts within a single character. For example, I specifically need to create the letter Ἀ with a so-called 'smooth breathing' (as seen here), but for the letter to additionally have a dot Ạ underneath (as seen here). Theoretically there are two solutions for this, but in practice they do not work for me (I have Word version 16.66.1 on mac 10.15.7). The first is to use "Combining diacritical marks" in "Advanced Symbols" from the "Subset" of a given font - the problem is that in my version of MS Word there is no such item as the "Subset" of a given font from which I could select "Combining diacritical marks". The second option, on the other hand, is to use a path: Insert -> Equation -> Accent and selecting from the list of possible accents the accent marks I need, the problem, however, is that in this list I do not have a choice of, for example, a dot under a letter, but only over a character.... I have attached below some screenshots illustrating this problem. Please help.