Final answer:
Data Transfer is the feature that facilitates the combination of log-level impression and click data for custom reach analysis, allowing for detailed and tailored insights.
Step-by-step explanation:
The feature that can be used to combine log-level impression and click data for a custom reach analysis is Data Transfer. Data Transfer allows advertisers to collect raw, event-level data from their digital campaigns, which can include detailed information on impressions, clicks, and more.
This data can be used to perform comprehensive analyses and generate insights that are more tailored to their specific needs compared to aggregated data reports.
For instance, an advertiser could use Data Transfer to analyze reach and frequency across different platforms or to understand the user journey more deeply by linking ad exposures to conversions.
The feature that can be used to combine log-level impression and click data for a custom reach analysis is 'Data Transfer'.