is it possible to set “Publish as Unlisted” as default?
I don’t think so. Last I knew the workaround was to publish first to a category that has limited reading access (like admin only).
You could post to staff and then unlist and move it.
This isn’t yet an option, but it makes sense to me to add it. I think that most sites that are publishing unlisted topics would prefer to have all their topics published as unlisted. I’ll try to add this as an option in the next update to the plugin.
If you update to version 1.7.9 of the plugin, publishing posts as unlisted topics is now a site-wide option. The setting is called ‘Publish as Unlisted Topics’. It is found on the Publishing Settings tab.
If you are using the new WordPress Block Editor, publishing posts as unlisted topics can currently only be set as a site-wide option. I will add an option for this to the Discourse Sidebar if it is requested. If you are using the Classic Editor, publishing posts as unlisted can be set either as a site-wide option, or set on a per post basis.