The feature to edit the task forms from the workflow designer in Office 365 came with the July updates for Nintex Forms.
For me one of the best features that came with this is the ability to include fields from the related item in the task form.
However you may receive an error when you try to publish the workflow.
Error similar like the one below:
Error publishing workflow. Workflow XAML failed validation due to the following errors: Activity 'DynamicActivity' has 54 arguments, which exceeds the maximum number of arguments per activity (50). HTTP headers received from the server - ActivityId: 2d403179-534a-44ab-8ecc-cd1bd18271ed. NodeId: . Scope: . Client ActivityId : 18ef3f9d-a0e8-2000-213e-a3414321b7c2. The remote server returned an error: (400) Bad Request.
This error is explained in flowing post Workflow XAML failed validation due to the following errors: Activity 'DynamicActivity' has ## argum... .
The issue is that for each task form that you edit two additional variables will be added, even if the tasks are using the same content type!
This conclusion is mine and I came to it via testing.
So keep this in mind when you design your workflows!