[SalesForce] Change master label of lighting component

Yes. You need to create a design file for the component:

<design:component label="Label For Component">
</design:component>

See the Add a Design Resource to Your Component Bundle section in the dev guide at https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/components_config_for_app_builder.htm

There is the Salesforce Lightning Inspector for Google Chrome that allows you to inspect the Lightning DOM, which will give you the namespace, name, and attributes for all Lightning components in a page. I know you asked for a Lightning App Builder way of doing this, but I've found this an easier way to inspect how a page a constructed. This method also currently even exposes internal chrome elements (e.g. visualBuilder:appBuilder for the Lightning App Builder), although compilation security will prevent you from being able to use those internal, undocumented components directly.