Toolset has an option for loading Bootstrap 4. Where does the source CSS file live? If I customize it, is there any risk it gets overwritten when a new release of Toolset comes out?
Solution:
No, it is not recommended to hack Toolset plugin files, any change will be overridden when you upgrade Toolset plugins.
So you can disable Toolset options for loading Bootstrap 4, then load your own Bootstrap 4 files manually