Very useful extension is Text Marker (Highlighter)

https://marketplace.visualstudio.com/items?itemName=ryu1kn.text-marker

Features:

• Highlight/Unhighlight text from both command palette or right-click menu
• Update existing highlight rules from the right-click menu
• Jump to the next/previous location of the same highlighted pattern
• Highlight text using a regular expression
• Case sensitive/insensitive text matching
• Whole/Partial text matching
• Highlighting colour is configurable
• Save highlights that will be restored next time you open the editor Highlight/Unhighlight text.