UI: Added many Blender's File menu entries to Session menu to Open/Save existing sessions

Description of feature

Added many Blender's File menu entries to Session menu to Open/Save existing sessions.

Checklist

Please check if your MR fulfills the following requirements:

• Unit tests have been added, if possible
• Documentation has been updated
• Build was run locally and any changes were pushed
• Lint has passed locally without error
• CHANGELOG.md has been updated

FYI: @awesome_dev_too