You are unable to see the ADHOC API Entity for a custom Cross Domain Report created from Analytics > Reporting > AdHoc Report in the SFAPI Data Dictionary.
SuccessFactors BizX System
Cross Domain Report is a newly developed feature for Adhoc Reports which is currently not supported by SFAPI.
Refer to KBA 2207695 for info on Custom Adhoc Report not visible in SFAPI Data Dictionary (Single Domain only)
AdHoc Report, Cross Domain, SFAPI , KBA , LOD-SF-INT-API , API & Adhoc API Framework , Problem
SAP SuccessFactors HXM Core all versions