Undoing diff hunks in NeoVintageous
The ability to revert a diff hunk was added in Sublime Text 4. You can access it through the Command Palette and the Context Menu i.e. right mouse click.
Command Palette → History: Revert Hunk
Context Menu → Revert Diff Hunk
For quicker access, create a vim NeoVintageous mapping. I like to map it as <leader>hu. This is the same mapping used by the popular vim plugin vim-gitgutter.
Command Palette → NeoVintageous: Open RC File
vim
nnoremap <leader>hu :RevertHunk<CR>Command Palette → NeoVintageous: Reload RC File
Jumping to diffs
You can jump between diff hunks with ]c and [c. See jumping to diffs.
Support for jumping to diffs was added in Sublime build 3189. In previous versions you need GitGutter.
Further reading
:help neovintageous:help [c:help ]c