What i would do to check if an attribute value is empty, for example in a password form, is to create a boolean variable and then a decision step with a small expression like
Based on the Boolean True or False you could input a new activity. Don’t forget to add the object as paramater and retrieve the object first though!
As far as I am aware there is no way to auto-check all of the attributes in a microflow.
You can consider adding the validations on entity level in your domain model but you’ll still have to do it for all of the attributes.
If you don’t want to validate on entity level, I suggest you download the CommunityCommons module and use the ‘IsNotEmptyString’ Rule to check each of the attributes.