The good news is that its easy to make a copy of a table and copy it to another App. When you are on the table home page for the test app on one of your new tables, use the "More ..." button to copy the table and it will guide you through to selecting the destination app.
The bad news is that if there are any Relationships, they will be lost on the Copy.
Hence for the most part I would say that 95% of all Quick Base development work is done in a live app "carefully". Often some of the work may be first developed and then tested in a test app and the re-done in the live app.
The last 5% might be done using a tool called "The Sandbox", but that tool is only available in the higher level plans and has limitations such that it is not that widely used as far as I know.
Quick Base may have plans to improve this in the future but I have not seen any public product development road maps for that at this time.
