Keep Notepad++ from automatically populating the search value with selected/adjacent text

There is no standard option to do this but you can achieve it by:

1. The harder way: download N++ sources and make your own N++ build with desired modification

2. The easier way: using AutoHotKey tool, capture Ctrl+F shortcut (with condition only if N++ window is active, see #IfWinActive directive ) so when it is pressed, send keys Ctrl+F, Backspace. Similar for Ctrl+H (Replace)

The AHK macros which work for me are:

SetTitleMatchMode, RegEx

;--------------------------------- Hotkeys for Notepad++ only
#IfWinActive ahk_class Notepad\+\+

; present 'find' dialog with empty field
^f::Send ^f{Backspace}  

; present 'replace' dialog with empty field
^h::Send ^h{Backspace}  

; another example: close document with either ^F4 or ^W
^F4::Send ^w

#IfWinActive

For details regarding AutoHotkey macro setup, please check steps 1-5 in this answer.

This problem has been fixed since 2019. I downloaded version 7.8.8 and found an option to turn this feature off in Settings > Preferences > MISC > Don't fill find field in Find dialog with selected word.