ReadonlyidStable identifier for this section, equal to the widget's Lumino id.
The move plugin uses this to persist which sections have been moved and to restore them to the correct panel on reload.
ReadonlytitleThe .jp-AccordionPanel-title DOM element rendered by Lumino as the
visual header of this section.
The move plugin attaches the jp-movable-section CSS class to this node
so that Lumino's context-menu selector fires when the user right-clicks
the header.
ReadonlywidgetThe content widget for this section.
A section entry returned by IMovableSectionSource.getSections.
Bundles the three pieces of information the move plugin needs to identify, display, and transfer a sidebar section.