Make the On My Mac account node the drop target when the drop target is otherwise invalid — when dropping nonlocal feeds (URLs, etc. from outside). This way you don’t have to be too precise — you can drag anywhere into the sidebar to add a feed.

NetNewsWire/MainWindow/Sidebar/SidebarOutlineDataSource.swift

@@ -195,10 +195,14 @@ private extension SidebarOutlineDataSource {
 	}
 
 	func ancestorThatCanAcceptNonLocalFeed(_ node: Node) -> Node? {
+		// Default to the On My Mac account, if needed, so we can always accept a nonlocal feed drop.
 		if nodeIsDropTarget(node) {
 			return node
 		}
 		guard let parentNode = node.parent else {
+			if let onMyMacAccountNode = treeController.nodeInTreeRepresentingObject(AccountManager.shared.localAccount) {
+				return onMyMacAccountNode
+			}
 			return nil
 		}
 		return ancestorThatCanAcceptNonLocalFeed(parentNode)