Gutenberg 23.9: Parent Inserter Fixes the Gallery UX

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Every editor I have ever shipped in has had the same quiet problem. You are inside a nested container — a group, a gallery, a set of buttons — and you want to add one more thing to it. The interface has to guess whether you meant to add a sibling, add a child, or replace the selection, and it usually guesses wrong. In Flash it was symbols inside symbols. In Director it was cast members inside sprites. In QuarkXPress it was nested picture and text boxes. Everyone who has ever moved a slide-out panel to add an image to a gallery already knows the feeling.

Gutenberg 23.9 finally quiets that particular problem for the block editor. It also brings a couple of Global Styles changes that will save any theme author or agency ten minutes a day. It is not a headline release — no new blocks, no data-layer overhaul — but it is the sort of thoughtful cleanup that separates an editor you tolerate from one you actually enjoy using.

I have been running it on a staging site for the twentieth of the month cycle and it feels lighter. Here is what actually changed, and what I would do about it before it lands in WordPress core.

What is actually new

Gutenberg 23.9 shipped on September 2, 2026, in the usual bi-weekly slot. The release covers three things worth an agency’s attention: a parent-selector inserter, a custom-style indicator in Global Styles, and a small but overdue theming set.

The parent-selector inserter puts a plus icon on the block toolbar’s parent selector. When you have an image selected inside a Gallery, or a Button selected inside a Buttons block, or any child of Group, Columns, Cover, Details, Media & Text, Social Icons, or Accordion, that plus icon adds a sibling directly. No more clicking out to the parent and reaching for the appender. For single-type parents such as Buttons, it inserts the right block on click. For multi-type parents such as Group, it opens a quick inserter. List and Quote are excluded because there the typing model already does the right thing.

The second change is the custom style override indicator in Global Styles. Open Styles → Blocks and every block you have actually customised now carries a small dot next to its name. A filter menu next to the search field lets you show only the customised blocks. The previous behaviour listed every registered block with nothing distinguishing the ones you had touched, which is a nightmare on a site with fifty registered blocks and eight of them themed. Screen readers get an announced “Has custom styles” for parity.

The theming set is smaller in surface area but useful. Axial block gap for Group lets you set independent vertical and horizontal spacing on flex and grid layouts inside a Group block, matching what Columns and Row have had for a while. Label element styling registers <label> as a first-class element in theme.json, so you can style form labels from Global Styles instead of hand-writing CSS. Citations, Inputs, and Selects are now exposed as Global Styles elements with typography and colour controls. And custom duotone palettes can now be authored inside Global Styles rather than relying only on what the theme ships.

Everything else is the usual mix — component polish, first-time contributor fixes, accessibility work. Nothing dangerous, nothing that changes the block markup model.

Why it matters for WordPress and WooCommerce people

Two of these changes will directly shorten client training. When we onboard a marketing team to a new block-editor site, the gallery-and-button question comes up every single time. “I selected the image, why does the plus button add a paragraph after the whole gallery?” The parent-selector inserter answers that question by making the correct affordance visible in the place the user is already looking. That is one less line of documentation, one less loop of hand-holding, and one less reason someone reaches for a page builder.

The custom-style indicator matters for anyone maintaining a design system on top of Global Styles. If you inherited a WooCommerce site and you need to know which block styles the previous agency touched before you can safely refactor theme.json, that dot-and-filter is not a nice-to-have — it is the difference between a two-hour audit and a two-day one. It also gives you a clean way to hand a themed WooCommerce site over to a client without them accidentally undoing your work: “these dots are what we tuned, do not reset them without asking”.

The theming additions are quieter but real. Label, Input, and Select styling from theme.json means WooCommerce checkout theming, contact form theming, and search-form theming stop needing a CSS override file for the basic cases. Axial gap on Group closes a genuine inconsistency — every layout container should have the same spacing controls, and until now Group did not. And custom duotones inside Global Styles matter for editorial sites that want a signature look on image blocks without shipping it as theme code.

Gutenberg 23.9 will most likely land in WordPress 7.2, following the same cadence as the 23.x cycle that fed 7.1. If you are running the Gutenberg plugin on production you get it now; if you are on core-only, you will get it whenever 7.2 ships.

What I would do (or not do) about it

On a client production site, I would still not run the Gutenberg plugin. That has been my line for years and I am not moving it for this release. The plugin exists so contributors and testers can shake bugs out before they reach the tens of millions of core installs; that is a valuable job, but it is not the job of a live agency site. Wait for 7.2.

What I would do this week is install Gutenberg 23.9 on the staging copy of the two or three sites where editors regularly complain about the gallery and button workflow. Sit with them for fifteen minutes, show them the plus icon on the parent selector, and watch whether their body language changes. If the answer is yes — and in my experience with this class of fix, it usually is — that is a data point you can bring to the next quarterly review when someone asks why you are not switching to another editor.

For themes and design systems, this is the moment to open your theme.json and look at three places. Are you styling labels, inputs, and selects with a stylesheet? Move them into the elements section. Are you using a Group block with flex or grid layout and forcing horizontal gap via a custom class? Delete the class. Are you hand-listing which blocks your team customised in a README? Stop; the editor is about to tell you itself.

What I would not do is rip out working custom-CSS for label and input styling just because Global Styles can now do it. Global Styles is the right long-term home, but if a WooCommerce theme has a battle-tested checkout stylesheet that your team knows, migrate deliberately, one form at a time, and keep the visual regression screenshots handy.

None of this is a headline. It is craft. And craft, sustained across a hundred small releases, is exactly the reason a serious CMS beats a slick demo — every quarter for twenty-three years and counting.