I reckon the Config/Xui/xui.xml is a good place to start with the default being:
<window_group name="dewcollector" left_panel_valign_top="false" controller="XUiC_DewCollectorWindowGroup" close_compass_on_open="true">
<window name="windowDewCollector"/>
<window name="windowNonPagingHeader" />
</window_group>
and that hooking up to the localization.txt for:
xuiDewCollector,UI,XUI,,,Dew Collector,,...............
Since your plan is to have 3 stages, that'll be 3 custom ones with different names and matching block name hooked up directly so far for window_group name and other locations using the above as a template.
xuiDewCollectorWE1,UI,XUI,,,Slow Dew Collector,,...............
xuiDewCollectorWE2,UI,XUI,,,Medium Dew Collector,,...............
xuiDewCollectorWE3,UI,XUI,,,Fast Dew Collector,,...............
and so on depending on how you want to do it.
I did something similar for the Wild West Mod but just wanted a variable helper so players could choose from two types. The Window name was just 'Water Collector' and their blocks had the customised title instead. It depends to what level of customisation you want.