Update the launcher UI to be extendable and modular

[ajbozarth]

Problem

Currently the launcher is very simple and restrictive. You can only add items to it that execute a specific command and choose what category they display in. You can't make more interactive items like search bars or rearrange the categories. This restriction has caused some groups to develop replacement launchers that add more features.

Proposed Solution

To start, this issue is for sharing and discussing potential designs and paths forward for improving the launcher. Looking at examples of replacement extensions, open issues and POCs discussing problems currently faced, and deciding the first steps. After some discussion and research I will begin working on a POC

Some initial ideas include making the launcher consist of "widgets" similar to the home screen of iOS or Android devices.

Additional context

This feature has been discussed in the Jupyterlab weekly dev calls, especially in the March 9th 2022 call. See the notes in the agenda at jupyterlab/frontends-team-compass#135 (comment)

[krassowski]

Related issue on the UX side: #3795

[krassowski]

Also #6202

[krassowski]

I wonder if we could make the launcher schema-first as we do toolbars so that it can be cusomized from user settings too. This could allow:

• users to re-arrange the widgets freely
• users to add widgets mapped to arbitrary commands as in https://github.com/trungleduc/jupyter_app_launcher
• developers to add widgets the same way they can add widgets to the toolbar and users would still be able to reposition them later

[ajbozarth]

Your comment reminded me I was still assigned to this, I was in the brainstorming process when my bandwidth to work on this disappeared. I am still interested in helping brainstorm the design, but others should pick this up.