The URL field on the REST task, cannot be expanded

Create a process. Add the REST task to the process diagram. Open up the Assignments section and add the URL: Click on Source dropdown next to the "Url" Data Input and then click on Expression. Input any text and click Ok. Save the changes. Open up the assignment section. Actual result The URL text is not shown entirely, and cannot be edited. Expected result The URL text is shown completely and can be edited.