Instance variables cannot be used as value for Filter Row in an Ingest instance.
This window lacks the option to use Instance Variables as a Filter Row, ie Date>=’VariableStartDate’

This is possible in TimeXtender Classic with business units (Project Variables) and widely used at the customer. Currently Instance Variables seem only available on Prepare instances.
We are using Dynamic Variables a lot for limiting the data load in Business Units in TimeXtender Classic.