Hi,
We continued this conversation in our support email, but I will post the first answer if anybody else is checking for similar question.
The backlog for Agile Boards is no default import option in eazyBI. You can check out community post on this topic here:
If you identify Backlog as a Status in Jira. You can use Status or Transition status dimension on the report to see issues in this status. Status dimension will give you only current data for issues. Transition status gives you any historical data of this issue.
Here is one report example in our demo account on Issue days in backlog: Issue days in selected status - Issues - Jira Demo - eazyBI
Calculated measure Days in transition status till now represents previous days in this status and also counts days from the last time an issue has transited to this status (Transition to status last date) till now.
If you need to have workdays, you can change in the measure function DateDiffDays() to DateDiffWorkdays().