Now that I've gotten your attention with a perhaps outdated click-bait title, I'll have to clarify Tridion Sites GUI extensions are definitely not dead. The Classic UI Anguilla extensions will continue with the Classic UI, which still has important administrative features that will be around for several more product releases! 

Rather I wanted to highlight that the much-anticipated Graphical User Interface (GUI) extensibility for the Graphene-based Experience Space UI will be part of the upcoming Tridion Sites 10 release.

I'll let others (or you!) share more about the "how" of GUI extensibility in Experience Space, especially as we get closer to the release. Here I'll talk about the "who" and some background on the why this GUI extensibility feature is different than the previous GUI extensibility.

Who is Experience Space extensibility for?

This feature is meant for customers who want to adjust the out-of-the-box experience to add additional screens, buttons, or functionality to the Experience Space user interface. Specifically this extensibility is for features that are rather customer-specific that haven't been adopted into the core Experience Space user interface (UI).

How does this differ from the Classic UI extensibility (Anguilla)? Why is it different?

Experience Space GUI extensions will be React-based since Experience Space itself is based on React, which is both a proven modern frontend framework as well as a great fit for our use cases. The user interface introduced with SDL Tridion 2011 was created when Asynchronous JavaScript (AJAX) approaches were already popular, so it uses libraries like Sizzle JS for selecting things (DOM elements) in the UI.

But that UI and its extensibility framework, internally dubbed "Anguilla," was architected and built before front-end frameworks like React (which was open sourced in 2013) or Angular (with its first version released in 2010) took over a good part of frontend development.

So in short, new extensibility has to be different. Otherwise we'd be building yet another vendor- and product-specific approach to backend web application development, rather than something a bit more familiar to today's frontend developers. 

However, I can appreciate the challenge of revisiting already-written GUI extensions in Anguilla. I'll note that having worked with frontend developers within and outside of RWS, including both React developers and long-term frontend Tridion Sites UI developers, I'm confident and excited at how the "Stages of Tridion (knowledge transfer) grief" will be that much easier with React.

To make it practical, I've seen .NET developers adopt React as yet another part of their skillsets (without necessarily having to become ECMA experts even) as well as our own Anguilla developers start pull requests after some onboarding. One gotcha I've seen with React development might actually be how easy it is to get started! 

How can we prepare for the new GUI extensions?

I recommend perhaps brushing up on front end development skills and taking an inventory of your favorite GUI extensions in the Classic UI. Keep in mind that if you mainly work with a specific Tridion Sites instance that some of your custom functionality might be hidden. Our customers and their implementers have done such a good job with extensions that certain custom buttons, lists, and labels just look like they're part of the product! This is where having your implementation team review and share the Add-Ons that are deployed to your Content Manager.

Also keep in mind that many of the Tridion Sites ideas on RWS Community have been added to Experience Space as out-of-the-box product features, first in Tridion Sites 9.5, the best release in the last 10 years, with more added to Tridion Sites 9.6.

Tridion Sites 10 should prove to be the best release ever since the last best release and I'm quite excited to see what we build to further improve the editorial and administrative experience in customer-specific ways.

Please leave a link or comment on the kinds of GUI extensions you're considering for Experience Space. On my side I'm working with the team to revisit the RWS App Store to prepare for our next generation of extensions!