Multi-file Output Model
Templates can not only produce single files, but in case of CustomPreProcessors conversion, they are able to produce multi-file outputs. When enabled, multi-file output allows the conversion to export one output file for each input file (including body injections).
An example for a use case of multi-file output is a wiki. You may want to provide a printable PDF of your wiki while also creating a statically rendered website from the same inputs. Multi-file output allows for the rendered website to not be a single page.
Injections for multi-file outputs have a slightly different mental model to other templates. Instead of rendering the injections once, they are rendered for each output file separately, meaning the injection can include code that is unique to each output file.
For example, a header injection could include accessing the navigation metadata (see below) to render the current position in a tree. The concrete implementation is left as an exercise to the reader.
Multi-file output is enabled on a per-template basis and is only available to CustomPreProcessors conversions.