With a list of zettel identifier, a query directives, or a search expression, a list of zettel is selected. Actions allow to modify this list to a certain degree.
Which actions are allowed depends on the context. However, actions are further separated into parameter action and aggregate actions. A parameter action just sets a parameter for an aggregate action. An aggregate action transforms the list of selected zettel into a different, aggregate form. Only the first aggregate form is executed, following aggregate actions are ignored.
In most contexts, valid actions include the name of metadata keys, at least of type Word, WordSet, or TagSet.