As I know, Modern Document library is not provide multiple files check-in/check-out features like we are do into our Classic document library. The Sample SPFx extension to demonstrate the functionality of multiple check-in/check-out documents.
git clone the repo npm i npm i -g gulp gulp
This package produces the following:
- lib/* - intermediate-stage commonjs build artifacts
- dist/* - the bundled script, along with other resources
- deploy/* - all resources which should be uploaded to a CDN.
gulp clean - TODO gulp test - TODO gulp serve - TODO gulp bundle - TODO gulp package-solution - TODO