Yes. Mixing wax melts is an easy way to create your own fragrance combinations. Vanilla can soften a spicy scent, a clean fragrance can brighten something fruity, and woods or amber can add depth to sweeter blends.
Start small. Use portions of two scents instead of filling the warmer with several fragrances at once. That makes it easier to understand what each scent contributes and prevents one fragrance from completely overpowering the other. Keep the total amount of wax within your warmer's recommended capacity. If you find a combination you love, write it down so you can recreate it later.
For a first experiment, try two compatible directions: vanilla with a fruit scent for a dessert-like blend, citrus with herbs for something brighter, or woods with a soft floral. These are ideas to test, not guaranteed recipes; the individual formulas will affect the result.
If one fragrance is especially strong, use a smaller portion of it rather than automatically mixing equal amounts. Change just one ratio on the next attempt so you can tell whether you prefer it. Keep the total wax amount consistent, and use finished wax melts intended for your warmer rather than adding loose perfume or fragrance oil to the dish.