Most of your interaction with the Explorer is through contextual menus, which are displayed by clicking RMB on an item in the Explorer's tree view. The available options differ depending on the selected and clicked item(s).
ON EMPTY SPACE
Empty space is only available below any currently open Packages. Clicking next to existing items is not considered empty space.
New Package: Creates a new empty package;
Open Package: Opens a file dialog to open an SBS file.
On a package
Right-clicking on a package gives you many options related to resources, saving and publishing.
New lets you create new graphs (Substance graph, MDL graph, function graph), bitmap and vector graphics resources, as well as folders for sorting content
Import and Link let you bring in resources
Reload, Save, Save as and Save a copy as let you save to disk or recall from disk a previously saved version of the package.
Publish .sbsar file and Republish .sbsar file let you Publish your uncompiled, unoptimized Substance graph, into an efficient and portable SBSAR file for us in other Substance applications and Integrations. Publish as Previous repeats the previous Publish action with the same options, skipping the options dialog for faster iteration. The toolbar contains buttons with the same functionality.
Export MDL Module and Export MDL Module Archive options let your export MDL graphs to compiled mdl files, for use in other iRay integrations. These options are only available if a package contains an MDL graph.
Export with dependencies is different from saving and publishing. It takes your SBS files, collects all referenced resources and dependencies and creates a self-contained package. The dialog lets you choose what libraries to gather, and if the file should be a compressed archive (7-zip). This is a good choice for sharing an SBS file with someone else, without worrying about missing dependencies.
Send to... opens a sub-menu letting you directly send your package to Substance 3D Sampler, Substance 3D Painter, Substance 3D Stager or Substance Player.
Copy copies the selected package.
Paste pastes copied graphs and/or resources into the selected package.
Close package(s) closes all selected packages
Compute Outputs forces Designer to calculate all outputs of all graphs in the package.
Show In Explorer... opens the location of the package in your OS' file explorer window
Dependency Manager opens the Dependency Manager window for the selected package.
Open Dependencies opens all dependenies in the Explorer (Substance graphs only).