Integrated Development Environments (IDEs) are available to use in your Domino project as a workspace. The type of IDE you prefer to use in your project may not be available as an option for you in every project.
IDEs are defined by the Compute Environment in use in your project. Not all Environments are set up to contain every IDE, so if you have just changed your Compute Environment and can no longer find the IDE the want, either revert the Compute Environment or choose another that does have the IDE you need defined. If you would like to edit your current Environment to add the IDE you want, instructions for that can be found in our documentation, here.