I want to use word completion in Ex mode, similar to using
Ctrl-N in Insert mode to complete the current word.
Suppose, I want to do a substitution:
:%s/<pattern>/<replacement>/gc. If the cursor is on the word to substitute, I could use
C-R C-W to paste it into Ex mode (command-line). However, sometimes the cursor is far away from the word to substitute, and here word completion would be beneficial.