>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #3576281. --> Reported by: [tim bozeman](https://www.drupal.org/user/2241356) >>> <h3>Problem/Motivation</h3> <p>Nested layout support in lb_plus relies on a <code>nestedStoragePath</code> string (e.g., <code>0/uuid/1</code>) that encodes the traversal path to a nested section. This path must be threaded through routes, forms, JS, event subscribers, and tempstore operations across 180+ code references. It makes nested layout handling fragile, hard to extend, and tightly coupled to <code>SectionStorageHandler</code> &mdash; a god-object that mixes concerns like path encoding/decoding, section traversal, block content loading, and tempstore updates.</p> <h3>Proposed resolution</h3> <p>Replace the path-based system with a <code>NestedAwareSectionStorage</code> decorator that wraps any <code>SectionStorageInterface</code> and provides:</p> <ul> <li><strong>UUID-based lookups</strong> via a <code>TreeIndex</code> &mdash; O(1) access to any block or section by UUID, eliminating path encoding/decoding.</li> <li><strong>Explicit bubbling</strong> &mdash; <code>bubbleChangesToRoot()</code> replaces the old <code>updateSectionStorage()</code> pattern of manually threading changes back up.</li> <li><strong>Scoped storage</strong> &mdash; <code>forLayoutBlock($uuid)</code> returns a view scoped to a nested layout block, so core forms using delta-based access work transparently with nested layouts.</li> <li><strong>Automatic service decoration</strong> &mdash; all section storages are wrapped via service decoration, so the nested-aware API is available everywhere without manual wrapping.</li> </ul> <p>This eliminates <code>SectionStorageHandler</code>, <code>nestedStoragePath</code> from routes/JS/events, and lb_plus overrides of core's <code>ConfigureSectionForm</code> and <code>RemoveSectionForm</code>. Core and contrib routes with a block <code>{uuid}</code> parameter work automatically with nested layouts via a <code>NestedRouteEnhancer</code>. Section routes use a <code>?section_uuid=</code> query parameter instead of lb_plus-specific route overrides.</p> <p>The <code>edit_plus_lb</code> and <code>lb_plus_edit_plus</code> bridge modules are consolidated &mdash; their functionality moves into lb_plus (registered conditionally when edit_plus is available) with update hooks to auto-uninstall the deprecated modules.</p> <h3>API changes</h3> <ul> <li><code>SectionStorageHandler</code> removed. Callers should use <code>NestedSectionStorageInterface</code> / <code>NestedAwareSectionStorage</code> instead.</li> <li><code>nestedStoragePath</code> removed from routes, events, JS, and contextual link parameters. Use UUID-based methods (<code>getPath()</code>, <code>getSectionsFor()</code>, <code>forLayoutBlock()</code>) instead.</li> <li><code>SectionToolIndicatorEvent</code> and <code>BlockToolIndicatorEvent</code> use <code>layoutBlockUuid</code> / <code>isNested()</code> instead of <code>nestedStoragePath</code>.</li> <li>Routes simplified &mdash; block operations use <code>{uuid}</code> only; section operations use core routes with <code>?section_uuid=</code> query parameter.</li> <li><code>ConfigureSectionForm</code> and <code>RemoveSectionForm</code> removed &mdash; core forms work via route enhancer + response subscriber.</li> </ul> <h3>Data model changes</h3> <p>None.</p>