Command Palette: consider nudges to find commands only available in one editor experience

[annezazu]

Pulling in feedback from a YouTube video I did on some 6.5 features (linking for the full context):

One bug that I think is still a bug is when using the search feature (CMD-K on mac) when I'm in site editing I can search and find the Customize CSS editor on the right sidebar. When I'm editing a page and use the search feature (CMD-K) I cannot search for CSS, Customize CSS is not a search result; I have to click on 'Edit Site' and then search.

Here's the current experience:

• In Post/Page Editor, no results when searching for CSS.
• In Site Editor > Templates, CSS is shown as an option.
• In Site Editor > Pages, CSS is shown as an option.

Here's a quick video:

CP.search.for.css.mov

Considering how much we're trying to unify experiences, I think there's something to be said for either opening the Site Editor if user perms allows it, showing a greyed out command (site editor only), showing a "search commands in the Site Editor", or something else entirely.

This touches a bit on how to show third party commands, design consideration wise #53192

I'm not sure how we balance this with increasing the command palette being contextual but I do think this is feedback to consider as we think about the future of the command palette, particular when it might get opened up everywhere #58218