The list columns of a report on Agent Workspace home page are configured in the "Select fields for list" of the report.
1. Log in as admin.
2. Get the sys_id of the particular report using inspect the HTML elements.
3. Navigate to "sys_report.list" and open this report.
4. Configure the Form Layout, adding the filed "Select fields for list[filed_list]" to the Form.
5. Disable the UI Policy "Make report config fields read only" which makes the field "Select fields for list" read-only on the form.
6. Edit the "Select fields for list" field, adding or removing fields.
7. Save the report.