Improve how list of field suggestions is displayed in the UI for `ContentTemplates` and remove `ContentTemplates` from feature flag
>>> [!note] Migrated issue
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Reported by: [hooroomoo](https://www.drupal.org/user/3688872)
Related to !218 !211
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<h3 id="overview">Overview</h3>
<p><span class="drupalorg-gitlab-issue-link drupalorg-gitlab-link-wrapper"><a href="https://git.drupalcode.org/project/canvas/-/work_items/3541037" class="drupalorg-gitlab-link">https://git.drupalcode.org/project/canvas/-/work_items/3541037</a></span> added the ability to link a prop of a component to a content type field. </p>
<p>This is a follow-up to improve how the list of suggestions is displayed in the UI. Currently it is presented as a flat list. We can do a nested menu structure and also update how the used field is displayed in the menu by removing the '(active)' string.<br>
This is the frontend counter part of <span class="drupalorg-gitlab-issue-link drupalorg-gitlab-link-wrapper"><a href="https://git.drupalcode.org/project/canvas/-/work_items/3547598" class="drupalorg-gitlab-link">https://git.drupalcode.org/project/canvas/-/work_items/3547598</a></span>.</p>
<p><strong>This issue also removes the Content templates feature out of the dev mode flag</strong></p>
<p><img src="https://www.drupal.org/files/issues/2025-09-23/Screenshot%202025-09-23%20at%202.39.54%E2%80%AFPM_0.png" alt="sc"></p>
<h3 id="proposed-resolution">Proposed resolution</h3>
<p>- Nested menu structure<br>
- Update how the selected field is displayed. Currently it says '(active)' in the menu item and it is disabled but we can either replace the '(active)' with a checkmark, or use blue text. Run by design?</p>
<h3 id="ui-changes">User interface changes</h3>
> Related issue: [Issue #3547598](https://www.drupal.org/node/3547598)
> Related issue: [Issue #3541037](https://www.drupal.org/node/3541037)
> Related issue: [Issue #3551339](https://www.drupal.org/node/3551339)
> Related issue: [Issue #3541000](https://www.drupal.org/node/3541000)
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