Default Statistic Custom Field
Introduction
In the Portal statistics, when a user adds a new chart, the statistic filter will
display the five default custom string fields CustomVarCharField1 to
CustomVarCharField5. You can customize them with your custom
string fields.

Customization
Create an override that overrides subprocess
createDefaultStatisticCustomField() in DefaultStatisticCustomField.p.json
process in portal. This subprocess return a list of custom string fields.
Follow instruction to create default custom fields.
