Currently, Search all notes (default shortcut: F6) focus the search field above notes and you can indeed show all notes containing a certain string.
Generally once you've filtered those notes, you want to find the actual string in each note. To do this, you must open the local search field with Search in current note (default shortcut: Ctrl+F) and then reenter the same string, and press Enter or use the up/down arrow buttons to navigate to the previous/next occurrences (not that Enter only navigates down, as Shift+Enter doesn't navigate up; but that's not the topic of this suggestion).
It would be nice to streamline this flow, by having at least an option to fill the note local Search field with the same string:
- Search all notes > enter string > press enter
- All notes are filtered and the local search field has been filled too
- Now, you can Ctrl+F and press Enter directly
Even better, adding a shortcut to search the next occurrence of the local search field without having to open the search panel with Ctrl+F would make step 3 even simpler. For instance, you could have F3 > next occurrence and Shift+F3 > previous occurrence (similarly to suggestion in Search highlighting and next could be improved).
Alternatively, the All notes search field could have its own previous/next arrows which allow you to navigate back and forth across all the notes with just Enter and Shift+Enter, or whatever shortcut you set.