Symphony.

If I filter the article list in the backend, by clicking on one of the headers, how do I clear that filter again?

I've got to checkbox fields that are displayed in the list, on for Online and one for Featured. Clicking Featured filters out all non-featured articles, rather than sorting. Is this the expected behavoir? To show all articles again, even non-featured, I've to to click on another header in the list.

Clicking Online sorts by "Yes" and "No".

how do I clear that filter again?

You can add ?unsort to the URL

Clicking Featured filters out all non-featured articles, rather than sorting.

Did you add the "Featured" checkbox after entries where already in the system?

Yes, the checkbox was added down the road.

Yes, the checkbox was added down the road.

I think you need to re-save all entries to give the checkbox field a value (I think this is listed as a bug - checkbox field created with wrong default value).

The problem is to do with how data is saved for fields. Each field has its own table. If a new field is added, that table has no data. When the sorting is applied, ORDER BY field_X.value or similar, you will only get entries returned that have a value, hence why they seem to be filtered out. Re-saving, as Lewis suggests, should solve the issue.