I wonder if someone can create a DEGIRO broker plug-in.

There are some unofficial API clients for DEGIRO's trading platform, e.g.
https://github.com/indiketa/degiro-java-client
https://github.com/drag0s/degiro

Some information for potential plug-in developers: DEGIRO doesn't provide demo accounts. A real account can be created within minutes. According to DEGIRO, 'You can register a free account entirely online within 10 minutes. DEGIRO uses derived bank identification to confirm your identity. This means that there is no complicated paperwork to fill in but you will need to make an initial money transfer to gain access to the platform. Please be aware the minimum of this transfer is £0.01.' (for UK)

Show me an official API, and then we can talk.

+1 for DeGiro API

It's the largest zero commission broker in Europe. Commissions from European IB brokers are ridiculous. Other EU brokers have no API.

DeGiro does not have an official API as of this writing, so getting an officially supported Zorro plugin is 99.999999% unlikely. The only APIs that exist are hack jobs.