Would you mind sharing what the URL is?
I tested external bookmarks with a URL that included spaces:
And I was unable to add it:
However, when I replaced the spaces with %20 I was able to successfully:
http://example.ab.ad.abc.com:8080/contactcenter/viewContent.do?externalId=144&sliceId=1#External- Standard Application
I think when I apply the "%20" to fill the blanks in the bookmark, my application can't read them, so less of a Jive concern, more on the application side.