Elingo’s The Wild Update Concept
Elingo’s The Wild Update Concept introduces various blocks to Minecraft that are expected to be featured in the Minecraft Bedrock Edition at some point in the distant future. You can start using them right away.
Elingo has added mangrove trees for Minecraft.

Clay bricks in the modification Concept of The Wild Update by Elingo (Elingo’s The Wild Update Concept).

Thus, mangrove wood can be processed into planks. The leaves of this tree are also available in MCPE. Here are all the blocks from the modification, including mud.
Feel free to attempt building a house similar to the one showcased by the developers in the MCBE screenshot.

Ah, and the most important thing. The game will indeed feature mangrove swamps. Here are a few screenshots.
Make sure to enable experimental settings.