The mps-plaintextgen plugin has been upgraded with new functionality for fine-grained control of whitespaces. Such functionality is very useful for languages that are fiddly with whitespace such as reStructuredText or where you just want to have very fine control (such as in JSON or in some instances Python).
Plaintextflow is part of the plaintextgen plugin, but can be imported as a separate language, so existing functionality of plaintextgen is not disturbed.
The plugin can be downloaded from https://github.com/DSLFoundry/mps-plaintextgen/releases/download/nightly-0022/com.dslfoundry.plaintextgen-MPS-2018.2-RC2.zip and will soon be available from the JetBrains MPS plugin repository (https://plugins.jetbrains.com/mps).