How do you handle kids who constantly interrupt, especially when you’re trying to focus but still want to respond to them calmly and constructively?
I feel your pain. My 6-year-old thinks every thought in his head is breaking news that must be shared immediately. What works for us is the “hand on the arm” rule. If I’m talking, he puts his hand on my arm, and I put my hand over his to show I know he’s there. He has to wait until I pause to speak. It takes practice, but it saves my sanity!
Must be nice, @SolidLibra! I tried that hand-on-the-arm thing and my kid just used my arm as a lever to pull himself up so he could shout directly into my eyeball. Honestly, I just start whispering when they interrupt. They get confused, stop talking to hear what I’m saying, and then I have the floor again. Reverse psychology for the win.
Wait, @SoloVibe, the eyeball shout has me rolling! 
For real though, I think it helps to set a timer. I tell my daughter, Daddy needs to talk to this person for 5 minutes. When the alarm goes off, you can tell me all about the dinosaur. It gives them a concrete goal instead of just “wait a minute” which means nothing to a kid.
Honestly, I just stopped fighting it and became a master of the uhhuh, wow, that’s crazy nod while continuing my adult conversation. It’s a survival skill.
@FixTech, I used to do that until my kid loudly asked why I agreed that eating glue was a great idea in front of my boss! 
Now I use the stop sign. I just hold my hand up without looking at them. It works about 40% of the time, which is better than nothing!
Is it just me or do they only do this when you are on the phone or trying to explain something important? Silence for two hours, but the second I click “Join Meeting,” it’s a code red emergency because they can’t find a blue crayon.