Grant a DBA Role, all the required privileges across schemas without granting sysadmin or account admin access in Snowflake?

This can be achieved using ROLE to ROLE mapping or commonly "ROLE Hierarchy"

For example, you have two databases, Marketing and Sales. And each of them have their own developer roles, Marketing_dev and Sales_dev

Your requirement is to have a developer access to all databases, Then all we have to do is grant these roles to the Global_developer_role that you can then assign to the new users

Granting a role to another role creates a “parent-child” relationship between the roles (also referred to as a role hierarchy)

grant role Marketing_dev to role Global_developer_role;
grant role Sales_dev to role Global_developer_role;

<slightly formatted the question for better readability>