If you need a field to be always visible on a form, but not always required, you can use Field Validation to make a field required based on certain conditions.
Use case example: Depending on the value of another field (e.g. type of contract) you may or may not be required to collect a certain document in an attachment field. With this setup you can achieve just that.
Here's how to set this up in this example:
Go to the field you want to be required in certain cases (Document)
Go to the Field Validation section
Add one condition group
Add two conditions to the condition group and make sure the logic inside the condition group is set to AND:
The first condition determines when the field has to be filled out (e.g. Contract type is New)
The second condition specifies that this field needs to not be empty in this case (i.e. Document is not empty).
Together, these two conditions will ensure that the field needs to not be empty when the other field is set to a certain value.
Add a condition outside of the condition group, and set the logic to OR:
Add the opposite condition to the first condition inside the condition group, to ensure that the field is always valid when it doesn't have to be filled out. (e.g. Contract type is not New).
Here's what that could look like in the configuration:
