For fields assignable to Item, the preferred UI control type is unclear. There are two choices in the field:

1. text field, with completion
2. drop down of all possibilities

#1 adds little overhead to the server even on large installations, and supports relative paths, but is forbidding for many users. #2 is easy to use, at least for smaller installations, but cannot render relative paths. We might like a hybrid.

https://wiki.jenkins-ci.org/display/JENKINS/Chosen+plugin is a possibility but might be too much for some browsers and it is not clear that it supports editable combos anyway.

Better might be an adaptive control which loads the item list asynch, then if the current value exists, show it; otherwise, or if an Edit button is clicked, switch to a text field view with completion. There can be a cutoff on the number of items displayed in the pulldown, e.g. 1000, before switching to the text field automatically.