You could make a custom Entity field, with type: Inline HTML. Then use a formula to produce the desired output:

'<svg width="1cm" height="1cm" viewBox="0 0 100 100"><circle cx="50" cy="50" r="50" fill="' || CASE {custentity_satisfaction} WHEN 'High' THEN 'green' WHEN 'Low' THEN 'red' ELSE 'gold' END || '" /></svg>'