During the last Nextcloud conference in Berlin, I had a presentation about the next dashboard app that will comes with NC15. You can find my slides here
This new dashboard allow any app developer to create his own widget that will be available to any user of the Dashboard app.
The interface used to manage your widget are now available within the core of Nextcloud.
More information can be find here:
I am available here, on IRC or by mail if you want to create your own widget.
Please note that you will need to get/checkout the last version of master to use this tool.