Filter data is currently stored as Base64 encoded persistent stream data, which is good.

For development purposes, it might be convenient to store property bag instead, so that it's easily editable. For example stream and bag:

<filter name="Some Filter" index="2" clsid="{AF469F88-4439-4B8B-86CC-24925C563CAD}">
    <ipersiststream encoding="base64" data="AAwAAA=="/>
</filter>
<filter name="Delivery Delay" index="4" clsid="{E7DC1EDC-9A89-47A3-AFAE-C3AF7A932A94}">
  <ipersistpropertybag>
    <property name="Delay" value="1000" />
  </ipersistpropertybag>
</filter>

Basically saving to bag makes also sense as an option, but stream is more reliable. It might make sense to save both and load from stream, or bag as a second chance. Anyway, I am going to add load from bag now, and the rest might be not worth the effort.