Thank you for the question! Currently, we are considering adding an option to schedule posts in the upcoming versions. In the meanwhile, you can use Zapier to set up an Integration with Buffer and Tribe. What is basically does is create a post in Tribe once a post is scheduled in Buffer. Here's the video- https://www.loom.com/share/787deda3876842078c59e10ae67fda13/5
Please note that you should delete the content scheduled on Buffer later. Otherwise, that content would get posted on your social media account. If you don't remove the scheduled post in 'Buffer', it will post it in the community as well as Social Media Account.
Let us know if you have additional questions!