"metadata is long" means that a parameter has long value?
If so, I think this is mainly jenkins issue.
AFAIK, it is GERRIT_CHANGE_COMMIT_MESSAGE only. Because this is multi-line text, others are single-line.
So StringParameterValue class should be replaced to TextParameterValue.
But it would not be solved. ParameterValue which is extended by both StringParameterValue and
TextParameterValue has 2 methods for description.
In Javadoc, getShortDescription() requires one-line string as return value. I think this is truncation spec
But, as of now, TextParameterValue which extends StringParameterValue does not have any overrided
methods for getShortDescription().
It means that TextParameterValue#getShortDescription returns the same value as StringParameterValue's one.
So, unfortunately, it is hard to solve this issue only by plugin fixes.
If "metadata is long" means a lot of parameters, it is also Jenkins issue.
Jenkins does not have the way to reduce the display number of parameters from plugin side.