In the September update for Power BI Desktop, Microsoft has finally added intelliSense to the M Query advanced editor. This is a great addition for learning the M Query syntax and seeing what functions are available without having to lookup the reference documentation. This feature is not available in the formula bar. Only the advanced editor will have the intellisense.
In order to get this new functionality, you will first need to download the latest version of Power BI here. Once you have the latest version installed, go to File > Options and Settings > Options. Select Preview features in the left navigation. Check the checkbox next to M Intellisense and select OK. Power BI Desktop will need to be restarted in order to see the newly enabled feature.
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