You can cross post to different communities via the two double/overlapping squares that appear under the headline of your original post.
- Create and post original post in community A
- Go to your posting and click on the two overlapping squares under the headline of your original post. Title, text, body. will be automatically filled in.
- Choose community B in the drop down menu you want to cross post to and publish it.
- Repeat steps 1-3 for additional cross postings to other communities.
There will be a remark and link to all cross posted posts/communities the same URL has been posted to.
Hope, this helps :)