When configuring a job, under "Post-build Actions", there's a field for
"Projects to build". It's a plain text field, and I think it would be very
helpful if auto-completion were available, so that it's harder to make a
mistake when typing in the name of the job(s) you want to be triggered
downstream. (If auto-completion is not an option, a select/option drop-down box
might be an alternative.)