Not officially supported, but this is how I tweak registers and journals (you can't get to journals and registers via the report manager). This assumes you are proficient with Crystal reports.

Find the Reports folder and look for the specific register or journal you want to modify. Make a backup copy of the file just in case you mess it up. Then use crystal reports to modify it as needed. Once you have a successfully modified report, make a backup copy of it as well. This is important because when you install product updates or do upgrades the format may be overwritten.