There don't seem to be many milio things to learn that are:

1 not obvious - not a fact you could read on the wiki

2 helps win - not some random trivia that never matters

3 specific to milio - not a point that fits a spiel about another champion

This is how I feel about sona as well (see sona guide) - the gameplan is pretty simple.

Maybe one thing that takes a bit of getting used to is how disengage focused milio's Q is. It's pretty obviously a disengage because it's slow, so effectively more range on ppl moving towards you fast than ppl moving away from you fast, and it knocks back. But despite how obvious a disengage it is I still find myself wasting it sometimes instead of saving it for when someone runs or dashes in. Not particularly subtle but it is important.

I'm partially writing this post because I checked the milio mains subreddit and all the posts are like funny milio names, milio art, etc. Not that that's bad but it doesn't seem like there's a lot to say about how to play milio.

There is one long pinned post, which has maybe a few points worth considering:

-standard enchanter runes, the only interesting thing is maybe with how far back and safe he plays teamfights you don't go conditioning idk

-e or w first? this is probably the only non obvious choice because both seem to benefit from skill points pretty similarly: E cd 18s->14s, shield 60->140, movespeed 15%->25%; W cd 29s->21s, heal 70->150, bonus range 10%->20%...idk we'll see what people end up doing

-relic shield every game is wrong, if anything go spellthief's every game it's the better item, maybe relic vs cait lux or something if you can never hit them. Shurelyas vs moonstone seems to lean towards shurelyas every game, maaaaaaybe in some really front to back game moonstone but that doesn't happen idk. Also idk milio seems like a high kda champ so good for dark seal, but only his passive really scales well with ap, and sofw and even censer are big spikes

(General item diversion: the post's 189% wardstone gold efficiency number is intersting, although the post doesn't say where it comes from - maybe it's mostly the 12% bonus ap if you have like 300 ap already? so idk I could see wardstone+blue elixer being good since typically by that point the game is about to end soon and you don't have enough time to save gold for last item deathcap and it's probably more of a spike than redemption even.)

-One general point they write "NEVER go straight to botlane" nah here's my challenger milio guide:

1 lock in enchanter

2 autopilot bot (this is your window to grab a carrot or cookie or something if your kitchen is close to desk) (herald fights are ok to go to)

3 ???

4 challenger

-Another general point "Build flexible. Not only with Shurelyas/Moonstone, but read the room and analize your team champs, then, buy accordingly. It doesn't serve much purpose to auto pilot and buy chemtech putrifier when there is no healing on the enemy team." nah staff of flowing water is a really good item, for a champ like milio who uses it well you can just get sofw every game

I got a bit sidetracked into the weeds of more general items/support points; originally I just wanted to show there isn't much to say about milio in particular. I guess the fact that most of this dicussion is of general support points itself shows there isn't much to say about milio. The post does correctly say he's very passive and disengage focused, which is important but obvious.

Maybe it's a bit weird to write 500 words to say you have nothing to say but yeah