You need to merge arrayData into your arrayIndex first, so your structure may look like this:
{ arrayIndex: [
{ text: 'test1', arrayData: { otherText: 'testData2' } },
{ text: 'test2', arrayData: { otherText: 'testData2' } }
]}
Now you may use a Table within a Table (sap.m Namespace). Be sure, to define your models and modelnames before.
<Table items="{arrayIndex>/}">
<columns>
<Column>
<Text text="Headline"/>
</Column>
</colums>
<items>
<ColumnListItem>
<cells>
<Text text="{arrayIndex>text}"/>
<Table items="{path: 'arrayIndex>arrayData', templateShareable:false}">
<columns class="backgroundBlue">
<Column>
<Text text="Headline arrayData"/>
</Column>
</columns>
<items>
<ColumnListItem>
<cells>
<Text text="{arrayIndex>otherText}"/>
</cells>
</ColumnListItem>
</items>
</Table>
</cells>
</ColumnListItem>
</items>
</Table>
You must use {path: '...', templateShareable:false} for your second table in order to work properly.