Thanks for the clarification.
One of the improved features should be finer control over how the Jupyter Find and Replace works. See here for some guidance on how you can adjust options. It should have an option to search through the whole document as someone was pointing out here.
If what is described there for how to adjust the scope of the search isn’t working, you may indeed have uncovered a bug.
I don’t know if it will allow what you want, however, you can still use NbClassic. See more about NbClassic in my answer here. It may allow you to access what you prefer more easily for now. Keep in mind though that is a branch of development that will not continue other than maintenance henceforth. And so you may want to start getting used to the newer tech before that branch is no longer useful as the components diverge too much and support for the infrastructure needed to keep that branch operating eventually becomes too much.