Yes, it is still not possible to keynote a detail made of just lines. You need detail components. But, if you are doing a workaround anyway, you may want to consider this other one:
A simple generic annotation family, with one label for a text instance parameter such as "Id" or "Key", and a rectangle around the label, so that it looks like a keynote tag. Then, load this family into the project, into the drafting view, and from the project browser find the family and use Create instance. Then select the annotation family and, from the ribbon, find "add leader". The "id" or "key" value has to be entered manually of course, and will not be linked in any way to the keynote file, but it can have the correct reference, if the users looks up a table of keynotes before entering the value.
See illustration.
