Approval summarizers are stored in the Macro [sys_ui_macro] table.

From the left navigation pane, select System UI > UI Macros. Summarizers use a naming convention of approval_summarizer_ + '<table_name> (for example, approval_summarizer_change_request is the summarizer for change requests, while approval_summarizer_sc_request is the summarizer for service catalog requests).

Each summarizer is written in Jelly script, which is used to define internal forms. The script is stored in the large XML field at the bottom of the UI Macro form.