With the default VS Code settings (i.e. editor.wordBasedSuggestions set to "true"), type:
int some_unrelated_variable_with_std_in_the_middle;
namespace std<enter>
Bug: "std" gets annoyingly auto-completed to "some_unrelated_variable_with_std_in_the_middle". We complained to VS Code a year ago (microsoft/vscode#31075), but they didn't provide a solution.