Let's assume that we have a situation in which the validator checks if the variable is filled. We cannot do this with the variable property, because there may be a situation in which you want to hide this variable and don't check it. In this case, to get the effect of visual "due" we will configure the above action. We add an action to the form. You should see the configuration window.  Image Added
We add the variable of interest to the parameter field.  Image Added
When we open the form, we will see that the variable given by us has got an asterisk:  Image Added
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