Update: Vim 8.2.4724 finally added this feature.

Highlights the current search match.

Uses the PmenuSel highlight group by default. To use a different highlight:

1. Type :hi and find one you like, e.g. Visual.
2. Put let g:current_search_match = 'Visual' in your vimrc/init.vim.

Install using your favourite package manager, or use Vim's built-in package support:

mkdir -p ~/.vim/pack/airblade/start
cd ~/.vim/pack/airblade/start
git clone https://github.com/airblade/vim-current-search-match.git
vim -u NONE -c "helptags vim-current-search-match/doc" -c q

Copyright 2021 Andrew Stewart. Released under the MIT licence.