Use nested collections

Collections can have parent and child collections. Dragging a branch preserves depth and descendant relationships while moving it within the same project tree. Cycles, unknown parents, and nesting under a protected container are rejected. Deleting a parent promotes its child collections to the parent level in their existing order.

The extension can target a project or collection before saving to the cloud. If a selected destination is no longer available, the protected Personal/Inbox fallback keeps the session reachable.

While dragging a collection, horizontal offset is measured in 18-pixel indent steps. Projected depth is clamped so it cannot go deeper than one level under the previous sibling or shallower than the next sibling. Dropping a branch onto one of its descendants is ignored and the tree stays put. Protected collections stay at depth 0, and the sortable list treats children of a protected collection as roots so they cannot remain nested under that protected container.

In the extension destination picker, destination:get returns a CaptureDestination (projectId and collectionId) plus the project tree, with nested collections indented 16 pixels per depth. Changing project immediately saves that project's protected collection if one exists, otherwise its first collection. If destination:set fails, the options page shows the destination-unavailable error and reloads destination:get so a missing collection does not stay selected. An empty tree shows a disabled Inbox placeholder.

• Drag a collection right to nest under the previous sibling, or left toward the root; if the drop is rejected, the parentId list is unchanged.
• Collapse a parent only when you need a shorter sidebar; hidden descendants stay in the tree and still move with the dragged branch.
• After a destination save error, reopen extension options and confirm project and collection match a live tree entry before the next cloud capture.