First of all, of course, it is added to our database as a feature request.
Secondly, I want to say that MarginNote is a very feature-rich app, and we have many things to work on other than this feature. There are many imperfections in MarginNote when it comes to Mindmapping, Reviewing, and document management. Sure, "technically" it may not take a lot of effort to fix this issue, but you have to understand that we also have many other issues to work on: some are more urgent and could help more people, some less so.
Also, when we change some features, we want to do it right. It is actually not just the problem of removing a limitation, but much more. When we remove the limitation, users would want to resize the nodes as they wanted - and at a certain point, we would receive requests to have different presets for the sizes because of the inconvenience of resizing the notes one by one. What makes this even harder to implement is that with the current mechanism, mindmaps with hundreds of thousands of nodes are pretty normal. When dealing with mindmaps that massive, coming up with a resizing mechanism that works at all levels isn't easy at all. I mean here is not that we won't work on this issue, but rather we have already thought about it and it would be a big update instead of a small one. However, considering the amount of work and thinking that it requires, we would like to have more time.
Lastly, we are sorry that your request may not be addressed as soon as you want, but that does not mean that we don't work on the issues and don't listen to our users' voices. MarginNote is improving because of its users' voices. We are constantly implementing users' requests and have made many popular updates such as title-links, OCR Pro, iCloud syncing update, etc. We hope that you could be a little more patient and tolerant and allow us to have some time to come up with something better.