From https://europeanspring.net/new-deal-for-europe/ - click on Constitutional Assembly. Starting on page 6:
The European Union must be governed by the people of Europe, and for the people of Europe. Today, the EU suffers from a deficit of democracy: unelected officials make decisions behind closed doors, where corporate lobbyists have far too much influence. European Spring will fight for a democratic Europe, where citizens enjoy fundamental rights and control the future of their communities.
i. A Democratic Constitution
We call to bring the people of Europe together to develop a new Democratic Constitution for Europe. The EU is currently governed by a set of treaties drafted by unelected diplomats and government ministers. European Spring will launch a series of citizen assemblies, traveling country to country to ask people what they want from a new European constitution. This process will culminate in a referendum requesting a Constitutional Assembly, composed of democratically elected representatives from across Europe, who will draft the new democratic constitution.
ii. Empowering European Parliament
European Parliament must have the power to represent the interests of its democratic constituencies — and to check the power of the EU’s unelected bodies. We propose to strengthen the European Parliament in several ways. Parliament should have the competence to determine how its members are elected. Parliament should have the right to initiate legislation. And Parliament should be able to elect the President of the Commission freely and democratically — and to dismiss the Commission and its President through a constructive vote of no confidence.