This is a feature or function that I think would be a huge help to players, for both utility and cosmetic reasons.
With a shovel equipped a player should be able to dig out a live sapling from a forest biome. (Ideally this would be done without disturbing the voxels though such that people could do it without tearing up forest biomes.) And move it.
The sapling could then be re-planted grow into a fully grown tree after some time and then be able to harvested for wood. This might help with cosmetics; simply being able to place trees in a castle in areas where you've manipulated the terrain. (Say a path with trees lining it on either side, or using them as natural cover to conceal a base.) Or could be used to seed forests in new locations.
Though I don't think forest farming was really necessary or economically viable in medieval times, its something players should be able to do. There might also need to be some check that players aren't seeding forests of palm trees in the middle of the polar region, such as the sapling dying if you plant it at the wrong latitude.
With the proper back end support it might open the possibility for modders to add in custom trees and add mechanics for orchards and fruit tree growing and harvesting; though that may be beyond the scope of this concept.