How to build a un-minified version of Shopware 6 administration scripts for debugging purpose?

Question

I would like to debug the following not-very-helpful error message when trying to save a custom CMS component in Shopware 6 administration layout editor:

An error was captured in current module: undefined
errorCaptured @ app.js?16504701226454027:1
Xe @ vendors-node.js?16504701221582962:2
(anonymous) @ vendors-node.js?16504701221582962:2
Promise.catch (async)
Ge @ vendors-node.js?16504701221582962:2
n @ vendors-node.js?16504701221582962:2
o._wrapper @ vendors-node.js?16504701221582962:2

When having such problems in the store front, I usually modify build-storefront.sh to call

npm --prefix "${STOREFRONT_ROOT}"/Resources/app/storefront run development

instead of

npm --prefix "${STOREFRONT_ROOT}"/Resources/app/storefront run production

Now I want to adapt build-administration.sh in a similar way:

The original line is

(cd "${ADMIN_ROOT}"/Resources/app/administration && npm clean-install && npm run build)

When I change it to

(cd "${ADMIN_ROOT}"/Resources/app/administration && npm install && mode=development npm run dev)

I would call

"dev": "mode=development webpack-dev-server",

vendor/shopware/administration/Resources/app/administration/package.json

I do not want to use the dev server and changed this to

"dev": "mode=development webpack",

No the build runs, but I still get a minified app.js as a result.

How can I debug the initial problem further?