Writing Roblox scripts from a phone, any decent way?

not really. Studio only runs on windows and mac, there's no phone or tablet version, so you can't test or publish from one. what people actually do is write the Luau in any code editor app on the phone, save it as plain text, and paste it into Studio when they're back at a computer. if you've got a PC at home, a remote desktop app lets you drive Studio from the phone. it works, but it's painful on a small screen. ok for small fixes, I wouldn't build a whole game that way.