Select Instant Highlight in the Search menu or press its keyboard shortcut to highlight all occurrences of the selected text or the word under the cursor, without using the search toolbar or panel. Highlighting persists when you switch between files. Use Instant Highlight with the same selection or on the same word to turn it off. If you turn on the “double-clicking a word instantly highlights all occurrences of that word“ search preference, then double-clicking a word also turns Instant Highlight on and off.
Only one search term can be highlighted at any time. If you use both Highlight All and Instant Highlight then using either command turns off the other. All other settings on the search toolbar are ignored. The instant search commands have their own Instant Search Options.
To change the color or underlining style used for highlighting search matches, customize the color palette and change the “Editor: Highlighted search match” color.
Search|Instant Incremental Search
Search|Instant Find Next
Search|Instant Search Options