This documentation is not using the current rendering mechanism and is probably outdated. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
In addition to the FlexForm, many options can be set from the Constant Editor. Indeed, there are so many options that the Constant Editor has been divided into three forms:
- Calendar Base (General)
- Calendar Base (Templates)
- Calendar Base (RSS)