The DRL Editor will be removed with Axon Ivy 11.3. JBoss is no longer developing it and is relying (like us) on VSCode.
We still support DRL Rules, but no longer offer a syntax highlighter in the Axon Ivy Designer itself. However, you can still edit the files. If you want syntax highlighting, you can open the project with VSCode and install the DRL extension: https://marketplace.visualstudio.com/items?itemName=jim-moody.drools