Answer
This isn't currently possible — there's no mechanism to send a client refresh request from an Event Action, Workflow, or Custom Command; the older Windows client had a force-refresh option specifically for Custom Menus (though not for events), but no equivalent exists in the web client yet. This has been raised as a community Idea given how commonly it would improve the experience of any data-changing event/workflow/command, so check current Idea-wall status if this matters for your rollout, but treat it as unavailable for now.