After you have confirmed that the custom field is in the workflow table, you can use this procedure to add it to a form.
To add a custom field to a form:
On the Navigation menu, click Administration ยป Workflow Type Configuration.
In Workflow Type Configuration, search for the workflow type to which you want to add a custom field by either using the navigation buttons at the top of the form or using the Workflow Type Search dialog box.
On the Fields on Form tab, in the Custom Fields on Workflow grid toolbar, click Insert.
In the All Workflow Custom dialog box, search for and select the custom field(s) that you want to add. You can select multiple entries by clicking your preferred rows while pressing either CTRL (for separate entries in the list) or SHIFT (for a specific range of entries in the list).
Click Save.
(Optional) Click the Form Designer icon in the toolbar to change the layout, edit field labels, and make fields visible/invisible, among other things.
Remove a custom field from a workflow form
Add a source field to a workflow form
Customize form elements using the Form Designer