I am working on the project Mediaco, which is built with the React SDK.
I want to know which file contains those buttons.
These are OOTB flow action buttons displayed for every assignment. They are most likely ingested at run time.
The buttons that you have highlighted are ActionButtons component. If you wanted to look at the code for this component, and potentially make customizations then you can override the OOTB SDK component by running…
npm run override
… and selecting Infrastructure / Action Buttons
This will create the ActionButtons component in the src/components/override-sdk/infra/ActionButtons folder that you can review.
Please see the following documentation for further details.
Overriding components (pega.com)
If you are looking for the code that makes up the demo Embedded and Portal modes then this can be found in the src/samples folder.