I wrote this up a while ago. Have been doing it for a couple of months. This relies on an outside service to do the syncing.
A DevonThink based productivity center
Beginning steps -
Under the Finder, create a Calendar Entries folder in a shared location, such as Dropbox or a LAN.
Under a desired location in a Devon database, index that folder. At the outset, the index, like the folder, will be empty.
In the Calendar Entries group under Devon, create a group of twelve months using Data | New from Template | Registers | Months.
Under January, create a group of days using | Registers | 1-31.
Copy that collection into each month, deleting the days that don’t exist, such as April 31.
Optional: After the month groups are populated, you could create groups consisting of weeks. For June 2022, group 12-18 into a group called “12-18” or, if you prefer, “Week 2.”
You’re now ready to go. Start in the group corresponding to today. Write new notes. Import new items from other locations. Copy and paste email messages. Do your work as you normally do, under this new environment. Add the current month to the Favorites location on the sidebar. Next month, add that month’s group as well.
Your work will be automatically saved to the hard drive or SSD Calendar Entries folder that you created, so that it will be accessible outside Devon. If you index that folder using DTPro on another Mac, your work will always be available and can be updated on the other Mac.
If you rename the file, that propagates under the Finder. If you move, combine, or split files, that usually propagates, but double-check. It can be hit or miss, mostly hit.
(Note: If you delete an item or a folder under Devon, it will not be deleted under Finder in the Calendar Entries folder unless you take a couple more steps. Just delete it manually if you want to get rid of it on all computers.)
