Currently downstream project are only identified through fingerprinting. It would be great that projects which are directly triggered by another project would be shown as a downstream job even without any fingerprinting. The information is available because the downstream job already shows the link to the upstream project. Thus I would imagine it should be possible to show the link also in the other direction without fingerprinting.

The reasons I suggest to show the downstream project also without fingerprint are:
1) Requiring fingerprinting makes it more difficult if the downstream project doesn't need any file of the upstream project. E.g. because of issue 11409 it is required to have a wrapper job which triggers a couple of other jobs. The wrapper job does not produce any files which can be fingerprinted. As a workaround, one can create a file (e.g. with the BUILD_TAG as content) to have a correct fingerprint, but that workaround shouldn't be necessary.
2) Currently matrix jobs aren't identified as downstream projects. It might be possible to address this using fingerprinting and I filed it as a separate issue: 13083. But using fingerprinting it is not clear whether the job or each configuration should be marked as downstream. Thus it might be easier to address the matrix issue by the suggestion described here.