We can toggle the VS Code Explorer's visibility with ctrl/cmd+b. Is there a way to toggle it so it becomes full screen using a keyboard shortcut?
As far as I know at the time of this writing, no, there is not. There's a command View: Toggle Maximized Panel, but there is no corresponding command for Views (things in the primary sidebar).
This was raised in multiple issue tickets (google "site:github.com/microsoft/vscode/issues toggle maximized sidebar OR view feature-request")
Allow to maximize Side Bar #95139 was closed as "by-design", but I think that was a side effect of the specific nature of the particular issue there (the issue raiser had moved a panel into the primary sidebar (view) area and was asking how to maximize that)
Command for maximize secondary sidebar (and sidebar) #152575 was closed for not receiving enough community support in time to get added to the backlog.
If you really want the feature, what I suggest that you do get it in the backlog is raise it again as a feature request, and then promote your feature request to your friends, colleagues, and on r/vscode, telling people to give the issue ticket a thumbs up if they would like the feature-request to get added to the backlog.