I have a feature proposal for futer releases concerning sitemaps.
Some of us combine a WP blog with galleries managed by backlight.
For WP there are plugins that generate sitemaps dynamically whenever there is new content in the blog.
I found a popular one that can also generate subsitemaps and even include external URLs: https://wordpress.org/plugins/google-sitemap-generator/
With a rewrite rule in .htaccess it can even make the sitemap.xml available in the site root while WP sits in a /blog/ subdir.
With a large number of backlight galleries it gets tedious to enter all gallery URLs into the plugin configuration dialogue.
But as external URLs can be entered, it should be possible to add the path to another .xml file containing entries for all the galleries. I believe Publisher and Backlight to have (nearly) all the information required to build it. It could be updated whenever a gallery is added or changed. The filename could be configurable. If the file is named sitemap.xml it would serve as a standalone sitemap for the galleries and backlight pages. If it is given another name, it could be given to the sitemap plugin to be combinde with the WP sitemap.
Would that be worth the effort?
After having looked at external generators I like the idea of being able to manage the sitemap generation on the own site.
I wish You all a good time over the holidays.