Thunderbird can act not only as a mail client, but also calendar, address book, tasks app and more, which gives new productivity opportunities – for example, you can very easily convert an e-mail into a task or event. One of the things Thunderbird currently lacks, however, is support for sub-tasks/hierarchical to-do. Let me show you this amazing feature on an example (using Nextcloud Tasks): On Bugzilla, this feature was requested 21 years ago: https://bugzilla.mozilla.org/show_bug.cgi?id=194863 There are no good desktop apps supporting caldav and sub-tasks that I'm aware of, and the only such app for Android is Tasks.org. In addition, it seems Thunderbird already supports necessary attribute: https://github.com/Betterbird/thunderbird-patches/issues/79#issuecomment-1465267112
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