Hi, thanks for the quick reply!
I’m not very familiar with Obsidian yet unfortunately…
Yes, I’m talking about Miro the whiteboarding app! 
It has a very nice interface for quickly drawing mind-maps which can spread out in 360° with nice shapes and arrows and colours!
Another iOS app with a good free-tier that you could try (to demonstrate good mind-mapping) is ThinkSpace - it’s also great for quickly expressing your ideas in a colourful mind-map that can branch out in any direction you want.
I understand that it must be difficult to change from the linear, left-to-right tree diagrams, to 360° branching mind-maps… but it’s absolutely critical for a mind-map to be capable of spreading out in a non-linear way, because you’re using it to try to capture your non-linear thinking!
Currently, MarginNote is an important part of my studying - but it’s awkward to jump between multiple apps for different purposes, and it’s not convenient having pieces of your notes on one subject in multiple different locations. To make MarginNote the best studying app, it must be able to cater for all aspects of studying, and that includes free-form, fast brainstorming/planning too.
Both Miro and ThinkSpace do this job very well, and I feel it wouldn’t take a huge effort to alter the MarginNote mind-map tool to emulate them more.
And then I can finally delete my other mind-mapping apps and do all of my studying inside MarginNote!
Thanks again,
Stu