Copy SQL Server Maintenance Plan between instances on same server

I have multiple SQL Server 2019 instances on the same server. I’ve created and exported the first instance’s maintenance plan, edited its exported DTSX file to change the instance and plan names to avoid name conflicts, and imported the edited DTSX via SSIS (and DTUTIL) on the same server.

Problem: I see the the both the original and imported plan in SSIS under Stored Packages > MSDB > Maintenance Plans, but NOT under the second instance’s Management > Maintenance Plans list in SSMS.