Changing things after the first build
You carry on writing in plain language. Every change is a build, and every build is a version.
The editor is a conversation. Write what to change in the same language you described the app in: “add a gallery page”, “move the contact form to the home page”, “add a phone field to the orders table”.
What the preview shows
The preview in the editor shows the last version that was built, so you see what you have just changed. It opens only after the app has gone live for the first time — before that there is nothing to show yet.
What it costs
Every change is a build: it is measured, charged and saved as a new version. The estimate shown before a change is lower than for a build from scratch, but a change is not free — so it is better to collect several requests into one sentence than to send five separate messages.
If a change did not come out the way you wanted, you do not have to ask for it to be undone. In the “History” tab you can restore the previous version in one click, without paying for another build.