I'm not sure if it's already been answered but, what does the: "Lock Forestry" option do (Like, what features or functions does it have?)?

Lock Forestry locks the creation of Forestry Resources (Only meaningful if you play Industries DLC).
Lets say you created a large patch of fertile farm land, but wanted to detail these fertile farm land with trees (Trees are usually abundant around farms in real life), what happens is that the game will destroy the fertile farm land with each tree you plant on it. The more trees you place on fertile land, the lower the fertility of that land. In the end, your farming building will start to complain about not enough natural resources.
In order to overcome this, Lock forestry (Credit goes to Quboid) function was created, and what it does is that when you have Lock Forestry enabled, planting trees won't destroy the fertility of the land, and vice versa.
When you want to create more forestry resources, then just turn off Lock Forestry, and start planting trees, then forestry resources are created on the land.

Thank you a lot for your help