I have tryed to find out how to set a default notebook for new notes, both on windows, and on android. But cannot seem to do that. I hope it is possible, if not, this is a feature request.
Yours,
Anders
You can do that with the templates plugin.
You can see a basic example here.
Thanks for a Speedy answer! I will try that. But it it seems like it will only solve parts of it on the windows app, not on the mobile app. which is what I use "on the move". But will try to implement it on the windows ap. 
Anders
Setup the template on desktop and the notebook ID will still be used to place the note when you use the template on mobile.
Thanks again! I have now created a template, given it the "template" tag. Sat it as default template. And on windows desktop it works, when typing alt + shift + N. it creates a new note in my "innbox" notebook.
But, So I installed the "new template" on android, and got the "template icon" in the app. When choosing that, I get the Template menu. I then choose to create note from default template (it does not work on mobile). But Create Note from template, and then choosing the tempate creats a new note in the default innbox notebook. Thus to create a new note inn default notebook, I have to go like this: > Template Icon > Create Note from template > Change title of Template > write whatever. = four operations.
Another way is just to go +=new note > Choose new Note >>write title > choose notebook on notebook meny > write What Not. Which is four operations.
The ideal simplicity would have been to have a toogle in settings, where one just defined as a default which notebook every new note automatically was placed inn. It would make it easier to use Joplin as a more direct capture tool.
Thank you so much for your help!
So for mobile, you will still need to set the default template. The plugin settings do not carry over between systems with the sync (e.g. different desktops or desktop to mobile). Once you do that, you can then just click on the plugin icon and select "Create note from default template" and it will use the template that you set as the default.
The note that could be set as a default note will prompt you for the title and a description before creating the note in the designated notebook that was selected (getting the notebook ID must still be done on desktop at this time).
Enter the information you want into the fields to populate the note immediately when it's created.
Simple, in this case, but you can extend the template structure quite a bit to even make it somewhat modular depending on how complicated you want it to be. I personally prefer simple in most cases.
I simply made a notebook called: -Immediate Since - is alphabetically prior to any letter, I always appears on top. Within that notebooks, I have things like: Daily notes, Billing notes, Cheatsheets, and Markdown Guide.