@praveen solution is the ideal.
But i’d suggest the following as a belt-and-braces approach if you’er not on Pro licensing:
1 = Inform your users a few days in advance there is going to be an update at xxxx on xx/xx/xxxx.
We find adding them to a WhatsApp group also useful.
Tell them they’ll need to sync everything BEFORE that time or risk losing it forever 2= Pick a time above that nobody is likely to be using the App, such as 1800 on a Tuesday 3 = At that time just add the extra columns.
Since that is the only bit that would cause their app to stop working. 4 = Wait a day or so to confirm all is ok.
If anyone is running an older version, you’ll see Appsheet writing data into the wrong columns.
Sort those people out with a direct phone call or email. 5 = Finally you can then, at your leisure, create all your rules and views
We’ve done the above with 30-40 user construction apps and it seems to work quite well