How to hide specific projects from global planning.

Hello All,
We have three distinct types of projects that we're managing within our company: maintenance projects, assistance tasks, and dedicated projects. we want the dedicated projects to be handled separately with start and end dates while keeping the maintenance and assistance activities more organized without appearing in the planning.

• Maintenance Projects: These are for tracking bugs, fixes, and related tasks. They are primarily for organization purposes and won't be part of the main planning.
• Assistance Tasks: Similar to maintenance, these are for managing new requests, enhancements, and paid services. They're also for organizational purposes and won't be included in the main planning.
• Dedicated Projects: These are the real projects with start and end dates that should appear in the planning.

Please help me on how to achieve this need.

Best Regards.