That tool has been available by support request for several years. They did finally put it into 2020.1. The setting to turn it on is in General Preferences. Any time I've used it (including now that it's in the core build), NS throws up disclaimers left and right saying you should run copies of reports before you do this because it might mess stuff up, they're not responsible if you mess something up, etc. Kind of making you feel like they fully expect it to not work most of the time. All that said, I've used it at least a half dozen times and never had any problems. I would definitely follow their advice and take snapshot reports before you do it and of course test extensively in Sandbox first. Also, you're likely going to run into some headaches with CTA and other currency considerations if you are moving subs that roll up to parents with different functional currencies. At a minimum, you'll need to tie out CTA to make sure it's right and re-calc your consolidated exchanges rates. If you're running multibook, that adds another layer of complexity. On the whole though, it seems to work fine.

thanks for the response! No multi-book for us, thankfully. And as far as these things go, our changes are relatively minor (famous last words...). but good call on the sandbox testing and snapshotting reports. I will get our accountants to run as much as they can, and I'll snapshot the consolidated exchange rates too

When you activate the feature, a big disclaimer message comes up about what they recommend you do before making changes. I'd probably do all those things if nothing else as a CYA. If something does go wrong by chance, Support's first questions are probably going to be if you did all those things.