Summary
The mangrove boat with chest cannot be crafted at all in the 1.19.0.20/21 beta/preview.

How to Reproduce
1. Get a mangrove boat and a chest.
2. Craft them together.

Observed Result
You can't.

Expected Result
You should be able to.

Original Description
I was testing out by playing survival when i accidentally noticed that the mangrove chest boat recipe does not appear in a recipe book