Hi  @robert_mandell ‌, I did a major sub-account restructuring for our institution (over 300 sub-accounts) and used the SIS Import features to upload accounts.csv files where I updated the parent account field.  This moves the sub-account along with all of the courses within it.  The more courses in it, the longer it will take.

For details on the formatting of the csv, find info on this document under the accounts.csv section...

SIS Import Format Documentation - Canvas LMS REST API Documentation 

I've provided detail information here in the community before and will try to track down that post to share with you. Here are some things quickly off the top of my head...

• Document your nested structure in a document or spreadsheet first
• Establish a standard SIS_ID naming schema to identify the hierarchy
• If you created sub-accounts manually (in the interface) you've got to first go into each one and manually assign it a SIS ID.
• Test your csv import files in TEST or BETA first.
• If you're moving it into a sub-account that already has LTI tools installed at that level, they will automatically add to the course shells that you move there. We ended up with a few that had duplicates since they had had the LTI tool added at the course level in the previous structure.

I'll see if I can track down that other information, but I wanted to get you an initial response quickly.