If you need a social media scheduling tool that support Trial Reels on Instagram, check out OneUp.
OneUp gives you the option to schedule and publish regular reels, as well as Trial Reels on Instagram:
Trial Reels let you test new content with non-followers first, hiding it from your main feed, grid, and Reels tab until you decide to publish it publicly.
Note that Instagram only allows Trial Reels for accounts with over 1,000 followers. If you have fewer than 1,000 followers, it will not work.