I want to schedule the sending of a monthly report in RE NXT

If you are using a Standard Report you can schedule it to run for your manager but they will need to log into RE to retrieve it as the only place you'll see it is in the system notification bell in the top right of RE. If you want the report to be emailed to them automatically each month you will need to either use Power Automate Flow or a third party tool such as @Red Arc's Workflow Agents. Workflow Agent is currently in EAP and I've talked with them about the desire to schedule deliver of reports via email.

Queries and Lists can't be sent on a schedule.

I recommend attending the May Product Update Briefings to hear of any updates related to automation, scheduling, and the like.

@Jack Wagner I recommend the Daily Gift Digest Notification Power Automate Template from the Template Showcase as that has links directly to the constituent and gift records for your manager. Just tweak it to run on a monthly schedule or at their convenience. Lots of people on here to help if you need it.

There is also a beginner's guide on that link if you need help getting set up with Power Automate. You can get a free developer license from Microsoft for a flow like this one.