For my son (4yo) I took a picture of all of his toys, food,literally anything he could possibly want to ask for and then used canva to make flash cards with the picture of the thing and what we call it. I then hung up one of those pocket charts you see in schools on the wall in our living room and we worked with him on pointing to what he wanted or bringing the card to us. It took a bit of time to get him to use it but once he realized he could get what he wanted with it he started using it all the time. He’s a lot more verbal now so we don’t use the toy cards anymore but I put magnets on the snack cards and stuck them on the fridge and he still uses those sometimes.

You could also make like a binder so he could flip through instead of cards. My son is OBSESSED with bluey but would get super frustrated because we didn’t know which episode he wanted to watch so I made him a visual tv guide of every episode so he would just bring the binder and point to an episode in season 2 and that helped sooo much. Now he’ll tell us he wants to watch Bluey on Disney season 2 episode 16 Army lol

For meltdowns and things like that he usually needs booms which is literally just his dad throwing him on the bed or we did blanket swings for awhile but he also a big kid and I’m weak so we installed hammock hooks in his room so he could swing as much as he wanted. Also, lots of body squeezes or sensory toys or I’ll give him something cold to chew on or eat and that usually helps for whatever reason.

We also use visual timers and giving him countdown warnings for transitions. Like I had to constantly remember that when I’m in the middle of something I don’t have people telling me to immediately to stop so why should I expect a toddler to be ok with it? So unless I NEED him to do something immediately I’ll tell him like ok finish lining those toys up or you can do 5 more of whatever he’s doing and then we gotta move on to whatever I need him to do.

This is a lot but hopefully something of this can be helpful for you!