In Mendix, the Accordion widget does not allow the FileDropper as a child. This is a platform limitation enforced by Studio Pro (widget nesting restriction), so it’s expected to see an error like “Accordion cannot contain FileDropper” when you try to place it there.

As a high-level alternative, you can recreate the accordion behavior yourself using a simple “show/hide section” pattern. The core idea is to use normal Containers (which can host FileDropper) and control their visibility with a Boolean state, instead of relying on the Accordion widget.

In practice, you model each “accordion section” as two parts: a header area and a content area. The header is a Container (styled like an accordion title) that the user can click. On click, you run a nanoflow/microflow that toggles a Boolean flag (for example ShowUploadSection = true/false) on the page object (or a helper object).

The content area is another Container that holds the FileDropper and any related fields. This content Container uses Conditional Visibility bound to the Boolean flag. When the flag is true, the content renders and the FileDropper works normally; when false, the content is hidden—effectively giving you the same expand/collapse user experience as an accordion, without violating Mendix’s widget restrictions.

If this resolves the issue, please close the topic.