We are using the TPD editor for target platforms which can be found at https://github.com/eclipse-cbi/targetplatform-dsl. It currently only works in Eclipse versions >= 2018.09, but can generate target definitions for any Eclipse platform.
It allows defining target definitions with a DSL and generating .target files from them automatically. During the generation, the latest versions of the selected features are selected and added to the definitions.
We are following a scheme that is used by some other Eclipse projects, e.g., EASE.
Tycho will use the file org.eclipse.capra.releng.target.target for builds. This file has to be manually overridden when a new target platform has been created.
When developing, any of the target platforms can be used by first generating a target definition and then setting it as the current target platform. This allows developers to check compatibility in different Eclipse versions.