MCreator issue tracker has been migrated to GitHub.
Existing tickets have been migrated to GitHub. Please open new tickets on the GitHub tracker instead. If you do not have a GitHub account, all feature requests and bug reports from forums are still considered and checked by the maintainers.
MCreator 1.8.0 was not even released yet, nor it supports 1.7.10 and there was never any tree generator. You can, however, define custom trees for Biomes in biome generator.