"Primary tabs" and "Secondary tabs" not available

The starter kit theme in radix 6, and hence your default subtheme, does not have explicit regions for "Primary tabs" and "Secondary tabs". Instead you can use "Header" region, which is below the "Navbar" and above the "Content".

Drupal 10 does not have core blocks "Primary tabs" and "Secondary tabs". It uses block "Tabs".

I suggest adding the following blocks to "Header" region:

• Breadcrumbs
• Status messages
• Help
• Primary admin actions
• Tabs

Yes, that's it. Thank you very much!