Don't panic
These are only warnings
Every year this is the same procedure
Just be patient until App Inventor targets SDK 36
Also you do NOT need a tool to manually increase the target sdk in the manifest. Just be patient and wait. No tool is able to adjust the behavioral changes, which are also required to adjust every year.
See also https://developer.android.com/about/versions/16/behavior-changes-16 and for next year https://developer.android.com/about/versions/17/behavior-changes-17
Taifun