The "shortcuts" feature referenced here was replaced by Prompt Suggestions in the 2.x Assistant (this was reported against 1.0.0-pre.x; the package is now 2.16.0-pre.1). Selecting a suggestion now inserts plain text into the chat input, so the described rich-text / greyed-button behavior on partial deletion no longer has a surface to occur on - the ticket's own expected result (deleting a shortcut behaves like deleting text) is now the actual behavior. The original repro was also editor-alpha-specific (reproduced on 6000.3.0a5 but not 6000.3.0a4 at the same package version), i.e. a transient UI Toolkit rendering quirk. Closing as no longer reproducible. Please re-file against a current build if a similar issue appears in the new chat input field.