Adding components to a feature via Drush
Update: there is a direct way to add components via Drush.

First, to list components drush fc (for features components) will list out all exportable components, including which, if any, feature they are currently exported to.

Next, drush fe foo_feature variable:foo_var views_view:foo_view will update, or create, a module named foo_feature. The output from drush fc can be used to populate the required component:name syntax.

Original answer

While there is no direct command, the quickest way to add components is by editing the .info file.

For example, to add a view foo_view, you would add this line:

features[views][] = "foo_view"


or, to add a variable that hadn't been added, you would add this line:

features[variable][] = "my_variable"


Once these have been added to the .info file, you can then run drush fu, and the additional components will be exported with your feature.

Update:

There is a command. See the below answer about the drush fe command.