No, it is not possible.

In Mendix, it is not possible to delete or create attributes of an object at runtime. The data structure in Mendix, including the attributes of an entity, is defined during the design phase and cannot be altered dynamically during runtime.

Once you have defined an entity in Mendix, the attributes associated with that entity are fixed. If you need to make changes to the data model, such as adding or removing attributes, you would typically do so during the design phase and then deploy the updated application.

Hope it helps.

If you are talking about the contents of an attribute, for instance, an object “Employee” and you want to fill or empty the “Name” attribute – yes, you can change those. 

If you are talking about creating an actual attribute, that is not possible in the runtime. If you have an attribute you may or may not need, you'll have to choose a different setup of your domain model. For instance, you can make a simple “Attribute” entity that has a “Name” attribute, and a “value” attribute, plus any other attributes you might need depending on the use case. With some smart logic you can make it behave like an attribute you created at runtime.

No, you can't remove an attribute at run time. They are evaluted at compile time. You will need to either create your own custom attribute or use another form of validation.