Is there any way how to get the ID of the space for the current day (and if it does not exist, to create it automatically)? 
I am making a small program for Slapdash (https://slapdash.com) that allows me to send text directly to favorite spaces from anywhere on my computer.
Does this help you accomplish what you need?
Almost, I guess? 
I want a route to today’s journal and if it does not exist, create it.
You can add some logic so it pulls today, it won’t create though.
I use that route to send stuff to today’s journal with Siri Shortcuts all the time. And I use /new/tomorrow everyday so the next days space is always ready.
I guess I could create a script that would get all spaces and then filter them, and if the journal for the current day is not found, then create one. However, I am afraid that it would be rather complicated for me and relatively slow to proces.
If it helps here is the Shortcut I use. Works like a charm and super quick: https://www.icloud.com/shortcuts/a9be713b13ef43a5a8f7ecaf4ea53c03
If you can, I would try automating the creation of tomorrows space separately with the url so you don’t have to worry about if the days space is created.
A very nice code! I have to do it JavaScript but I always admire MacOS`s tools like Shortcuts, Automator, BetterTouchTool etc. On Windows, it is much less user friendly. Luckily, I have an older Mac to look at your code!
Just adding my support for this – would be a huge unlock for building tools on top of Kinopio.
with the release of merging/consolidation regular and journal space types I guess this isn’t needed anymore? The best approach is to get the most recently created spaces and sort them by space.createdAt via the public API endpoints GET /user with an authorization header or GET /user/public/:userId (you can get your user id in settings → general → account → developer info)