You’re right that chord diagrams at the start of the flow won’t appear if you turn on the option to show them after you have already overridden the first page: like all automatically-generated frames (flow headings are the same) they will only appear if the page has no overrides.
If you like to do things like add a graphical logo to the first page of your layouts, you should do this by editing the page templates rather than by overriding the actual page in the layout. There’s an excellent series of videos on YouTube that goes into great detail about managing page templates (they were called “master pages” when the videos were put together, so there’s a slight terminology mismatch to be aware of).
You can’t directly edit the chord diagrams at the start of the flow, so you should temporarily show them again in their normal places in the music (using the options in the context menu for the affected player(s) in Setup mode) to edit them.
Yes, @topjimmy, is it possible you’re not running the most up-to-date version of Dorico? The current version is 4.2.0 build 1092. Check the version number that appears at the bottom of the Hub window, or in the About Dorico dialog.
We don’t anticipate there being any way to exclude particular chord diagrams from the chords used frame in the next update, but we know that it is something users would like to see.
