Dynamically growing forms are a bit of a tricky thing to build in Retool but there are a bunch of different ways to approach the problem. Here's one example where using a JSON Schema Form is suggested. You might also try using a List View in your form, to which you can dynamically add rows. If you search for examples of List Views on these forums you should be able to find more ideas!
Curious to know more about what you've found so far!