Hi @noe1995,
I believe, as @rfeigel expressed a well, that you want to write into the DB only under certain conditions. There is no way to literally block access to a node if the extension is installed as the DB Writer is always installed alongside the DB Loader.
Though, a better approach would be to not block access to the node but i.e. require credentials. The awesome Selenium Nodes got one which resets when the workflow is loaded. If the DB credentials are stored in a file that is specific to the users who logged in on Windows, you can programmatically determine who only got read and who got read/write rights.
Here is an example workflow. Please bare in mind that this is really just a showcase! It is also imperative to understand that the user credentials should always be saved only temporarily but not permanently as the “new default”
User Name: user0
User Name: user1
In case the credentials are stored in a local file i.e. in the users home folder, permanently saving the default should theoretically work as upon reset the file is read again each time.
PS: I added two more options to evaluate and showcase the options at hand. The most viable approach is the one using Credentials Configuration as the password is reset after the workflow got closed.
Best
Mike