This other application is also an R-app? Because RDS and RDATA only work in other ones. Normally if you save it correctly, you should just be able to import it without issues from one R script into another. Here is a guide:
If you want to import data into an app other than R, you should save the data in a more commonly supported format like JSON, CSV, ... For lists JSON is a good choice. If you still get stuck, try posting a reprex here for more details. A reprex consists of the minimal code and data needed to recreate the issue/question you're having. You can find instructions how to build and share one here: