The imposition action in Switchboard allows to log the imposition process.
Go to pdfToolbox>Switchboard>Arrange>Impose. You will find the 'Runlist Debugger' in the dropdown like shown below.

When 'Runlist Debugger' is checked and you execute the Imposition process, a log window like the one shown below appears that contains the information on Imposition in 'INIT, START, END' form based on your runlist configuration and imposition scheme.

Loops are shown there as well and if there are the derived values of Variables listed. Important to note is that the Runlist Debugger is shown as long as any imposition is executed - no matter where (e.g. Process plan or test mode within a process plan).