Yes dry mustard can be used in place of Dijon Mustard.
When you have a recipe that calls for Dijon Mustard but you have no Dijon Mustard then you can use dry mustard which is mustard powder.
In fact you can use any type of mustard in a recipe that calls for Dijon Mustard but the dry mustard which is mustard powder tastes more similar to Dijon Mustard.
I keep a lot of dry mustard on hand because it lasts a long time and use it a lot in recipes.
Dry mustard has made the recipes turn out just fine when the recipe called for Dijon Mustard or other mustard.
When a recipe calls for Dijon mustard and you use dry mustard you use 1 teaspoon of dry mustard for 1 tablespoon of Dijon Mustard.