Hi and welcome @Matthew1988 !
That is functionality that was recently added in 2.5.0 that will be released on December 15th. I think you’re using 2.4.0? At the top right corner of the documentation pages you can see and change the openHAB version for which the documentation is shown. In the mean time you can install the 2.5.0.M6 milestone release which is already very stable and has this functionality.