Among the previous suggestions in this forum that I'm really fond of is the idea of "Layout Viewers" ("Layout Viewer" control ), which would allow you to define an entire layout block in one place and display it throughout the database.
Now that we have card windows, we are very close to that - in fact, the only UX difference between the proposed idea and the card window is A.) Card windows have minimum size restrictions, as mentioned in a previous submitted idea (Reusable Card Windows ) , and B.) Card windows are modal - you can't interact with the underlying window while they're open.
Since the first of these has been suggested already, rather than bury the suggestion in that thread, I'm suggesting the second here.
By removing the modal behavior of card windows, it would be possible to have reusable palettes or any other layout element which could be created and edited in one place, and then used in as many different places throughout the database as desired, and all occurrences would always be up-to-date with changes made to the one original source layout. For instance, you could define your navigation buttons on a single layout, then display them on the top of every other layout. Want to add a button, change the color of all the buttons, or change the script one button calls? Simple, just edit the master layout, instead of the current process of having to make the change separately (or cut & paste it) to every single layout that has the navigation buttons.
We already have something else that is close to this, too - "floating document" windows. The only problem is floating document windows retain the title bar and are positioned independent of the parent window, which, together, keep them visually distinct as a separate document windows.
So we have one window which can stay in front non-modally but requires a title bar and is not related to the parent window's position, and we have one window that can stay in front, requires no title bar, and is related to the parent window's position, but must be modal. So why not one that can stay in front, without a title bar, positioned relative to the parent window, non-modally? It's so close to what we have already, but adds functionality we could really use that we don't yet have.