[brianogilvie]

To expand on Sascha's explanation: you can define a default single-action list in the Data tab of Preferences, so that when you Clean Up, any action in the Inbox that has a context but no project will automatically be added to your default list.

There was a very long thread some time ago on whether single-action lists (at the time, called singleton projects or "buckets") were a good idea or the spawn of the Devil. Those in the latter camp had two (mutually exclusive) arguments: (1) A single action is conceptually on the same level as a project, so you should be able to put them in folders and see them in the sidebar. (2) A single action can't be planned, so it should not appear in Planning mode at all, but only in Context mode.

Those on the other side responded as follows: To (1), that the conceptual elegance would create a huge mess, as the sidebar and project list got stuffed with a whole series of single actions that could not easily be hidden. A single-action list allows you to hide single actions by collapsing the bucket in the outline. To (2), that not showing single actions at all in Planning mode would make it impossible to use the Focus command to include them.

I'm among those who think that Omni did a pretty good job with single actions. I have single-action lists in many of my folders (to use while focusing) plus a default one for those actions that either really are miscellaneous or are not worth the time to categorize.