Sounds like you want to use HTML Decoding. Luckily, this is really easy in Mendix!
Download the CommunityCommons module from the appstore, if you haven’t done so already. (IMO this is a go-to for any app you make, but that’s just a side note).
Once that’s in your app, you can use the “Call Java Action” in a microflow. Select the Java Action “HtmlToPlainText”, and use your <tr>
<th style="padding: 5px">Categorie</th>
<th style="padding: 5px">Vraag</th> as the input parameter. It should output with your tags, and any other decoded HTML you had in there, to be used in the rest of the flow.
Hope this helps!
Luke, I think that that java action uses javax.swing.text.html.HTMLEditorKit to convert the arg to plain text, so you’re going to loose all the tags. Try implement commons/lang3/StringEscapeUtils, it has what your after