I’ve hit upon a useful application of the “outline” document type. DTPO is the control-center for my work, and I have a number of databases. I usually create individual databases for large general purposes or projects.
To keep track of tasks that I need to do relative to the projects and/or the databases, I create a “Data > New > Outline” document and name it so that it floats to the top of the group list (usually “** Work Plans”). With that group selected, I use ctrl-cmd-N to create individual tasks with their state showing. I added a comment to top level “**Work Plans” group in the Info panel: @work_plans.
Over in the side bar I created a “Work Plans” smart group that looks across all open databases for “Comment Matches work plans”. This picks up all the individual “**Work Plans” outline documents and their subdocuments and shows me at a glance what needs to be done across all the open databases. I use the “Split” view with this.
(Unless a database is open, the side bar smart group will not know about these outline documents.)