FieldWidgetAction does not show the button on Select fields

Problem/Motivation

When you set a sub-form element to the select type element, it just doesn't show up. This can be seen in this issue 📌 Create 'ListInteger' FieldWidgetAction for AiAutomatorType LlmListInteger Active .

Steps to reproduce (required for bugs, but not feature requests)

Use the issue above and select "Select list"
The button does not show up.
For checkboxes, textfield etc it does show up.

Proposed resolution

Find a solution to make it show up.