Improve error messages in store

**Description**
Currently data lacks proper import support.

**Proposed solution**
Add configurable import with sensible defaults.

**Priority**: Low/Medium

No file, test, or entry point is identified. First locate the store implementation and any existing import handling, then clarify which data sources and configurable defaults are required; done means imports work with the agreed defaults and relevant error messages are covered.

Written by the indexing model from the issue text.