Actually...There is a solution to this.
Create a hidden field, call it say "Flow Designer Mandatory", consider how many functions you want from this, if there's only one then a checkbox will do.
But lets say you want differing mandatory fields at differing points in the flow. Then maybe a select box with multiple values, one for each stage of the differing mandatory stages.
Next create a client script, "on load" which checks the value of that field and will make mandatory when a user views.
Then use the client script to make the fields mandatory.
Like this.
In this case my trigger wont be hidden, I'll use a new state condition, the same as the select box mentioned above. But all we're doing server side is changing the value of a field (which can be done by the flow (update record) and also for my use case, manually, its the mere fact that that feild has a value of my detirmination that I can use the client script to onload, check for that value.
Here I have set state to resolved on a CSM case at the end of the flow. could just have easily set my hidden checkbox "Flow Designer Mandatory" to true. whatever the trigger, its the flow that triggers it.
Now a simple client script, if my new field has the values I want, then set the fields I want as mandatory.
Of course I have an "if not" condition to clear the value, should the record be moved out of that state.
