I could often use a double dashed/dotted barline. Can't do it with Sibelius 8.7.2.
In the main forum, we've been told that number of requests will be taken into consideration when prioritising feature additions to forthcoming Sibelius versions.
If we take this seriously, we must be careful to upvote selectively. Vote for the ones you WANT, not just anything that doesn't seem a bad idea!