Pluto is that app for me coupled with a simple portable install.
Installing on windows (workday I'm consigned to flames of woe) is simply a matter of downloading portable install .zip file, a simple startup .bat script[0], 'add Pluto', 'import Pluto' and finally 'Pluto.run()'
I now have an Observable-like[1]notebook with all the Julialang goodness without running an installer
[0] my julia.bat looks like:
@echo off
@REM see https://docs.julialang.org/en/v1/manual/environment-variables/
@REM %%1 is the project directory
set JULIA_PROJECT=%1
set JULIA_DEPOT_PATH=%~dp0JULIA_DEPOT
set JULIA_BINDIR=%~dp0julia-1.7.0\bin
set PATH=%JULIA_BINDIR%;%PATH%
%JULIA_BINDIR%\julia