No because that isn’t available in the auto(why it is called that)sandbox. This functionality is only available in the full sandbox function of avast Pro or avast AIS.

So you can’t pre-select a file/application to run sandboxed, if avast decides that it should be run sandboxed then you get the pop-up (see image), there is no way to also check the Remember my decision for this program (greyed out, inactive). so you can’t elect to run this program always sandboxed.

Your reference in the knowledge base article is actually for the Sandbox (full) and not the autosandbox information which starts below that paragraph you quoted.