I rely on the Outlook set-up using categories religiously. I use Outlook tasks but on my mobile devices I use TaskTask which does well syncing with categories.I am also an Outlook 365 user, but in the GTD official setup guides, they only go up to "Outlook 2019". I also wish to sync my Outlook 365 desktop with my Android phone, and of course, keeping as much of the GTD format in tact. For the past 10+ years I have followed two companies that have led in this space of GTD synchronization between desktop and device: CompanionLink - https://www.companionlink.com/ and Pocket Informant - https://pocketinformant.com/ With the Outook 2019 GTD setup guide, they assume that you are wanting to use Microsoft Todo for your tasks, but I just don't see why I can't use my native Outlook tasks? Why would I want to complicate things by adding in an extra tool if I don't have to? Because of this, the GTD outlook 2019 setup guide has you create task sub-folders, instead of using categories, because apparently categories do not sync in MS Todo. Any suggestions much appreciated.