Input Methods for Anceint Greek (and other diacritic heavy languages)

Let me start by saying that I'm well aware that there's a keyboard layout for Ancient Greek. My issue is that Ancient Greek is a diacritic heavy language, and you can get up to 3 diacritics on a single letter (and not very infrequently, but two is more common). In the current keyboard layouts for Xorg, you have to type all of your diacritics before the letter, and only when you press the letter you can see the result. For example, if I want to write ᾆ, I have to type ][:a. Since Ancient Greek doesn't have keyboards with those diacritics printed, you have to memorize the keys and type them in the correct order. What I'm looking for is a way to type the accents after the letter, without any particular ordering, and have them appear one by one. What I mean is that typing ᾆ would look something like this: ἀ -> ἆ -> ᾆ or ᾶ -> ἆ -> ᾆ This created the rather strange situation where typing polytonic Greek on Android is easier (but still somewhat slow) than on Linux or on Windows. Any help will be appreciated.