React extensions can be built using pluggable widgets: https://docs.mendix.com/howto/extensibility/pluggable-widgets
Angular based extensions could be done in the Mendix Widget framework, but requires a little more knowledge on the Mendix widget structure: https://docs.mendix.com/howto/extensibility/widget-development
https://docs.mendix.com/howto/extensibility/pluggable-widgets
https://docs.mendix.com/howto/extensibility/widget-development
These shall help.