My question is whether I can keep a search box each view in parallel. I often have to search for separate things in both views and it would be a great relief if I didn’t have to type everything twice every time.

One option is to take advantage of Notepad++'s bookmarking feature. Use Ctrl-M to pull up the Mark dialog box and enable the Bookmark line checkbox. Do the first search as a “Mark”.

Switch to the Find tab and enter the second pattern you want to search for and do the search.

Close the find/Replace/…/Mark box.

Now you can use the F2 function key to jump to the next bookmarked line (the first pattern you searched for) and the F3 function to jump to instances of the second pattern. Shift+F2 and Shift+F3 both work and will go to the previous pattern 1 or pattern 2 as desired. Ctrl-F2 will toggle bookmarks on a line. I like this as I can do a mark to bookmark lines in a file I. As I then visually inspect the lines and if I no longer need to deal with that item I do Ctrl-F2 to switch the bookmark on that line off. The marked highlighter makes it easy for me to see where on the line my search had matched.

Also, I don’t know if you are aware that the Find what field in search box is a drop down list of the most recent searches. Click the ˅ down arrow at the right side of the Find what field. You don’t need type everything twice but instead can pick out recent things you have searched for from the drop down list.