The PartTools package is a set of utilities used by modders to import 3D models into KSP. PartTools also includes the coloranimation tool and the KSPAssetCompiler tool (for compiling asset bundles).
PartTools have been updated and re-compiled for Unity 2019.2.2f1 for KSP 1.8 to include all of these tools in one unity asset bundle.
It can be downloaded here.
Uninstall the built-in TMPro from Unity 2019.2.2f1 - Go to Window - Package Manager. Select TMPro and uninst