Hangfire Dashboard is slow to enqueue or delete multiple jobs

If I open for example this url

/hangfire/jobs/scheduled?from=400&count=100

and I select all and press delete, or enqueue now, looks like it's processed one by one, because it's very slow.
Is there a reason to this slow performance?

Reproduce the issue at /hangfire/jobs/scheduled?from=400&count=100 by selecting all jobs and trying Delete or Enqueue now. Trace how the dashboard handles these bulk actions and determine whether completion can avoid processing jobs one by one; done means the reported bulk operations no longer exhibit the described slowness.

Written by the indexing model from the issue text.