Thanks all for all comments!
Let me address some of the more overarching questions and comments you've written down.
I know a lot of duplications of code is there. There is between RenderableTimeVaryingFitsSphere and RenderableFieldlinesSequence as well as between RenderableTimeVaryingFitsSphere and RenderableTimeVaryingSphere (Where inheritance and implementing support for the dynamic sequence downloader is clashing).
I will make improvements around for the next patch release.

Ylva asked about the GUI issue I've raised concerns about . I find that to not be an issue anymore, I think mainly since I redid the onChange function declarations and addProperty calls in the right order, making sure onChange was declared before adding property.

The scale on the fieldliens: I need to scale them up with the size of the Sun. Is there a different place I should do that instead, or do I need to implement a property?

Naming: We landed on Today's Sun. As the rest of the profile have good one word names, it was difficult to come up with one that would describe the general whole purpose with it. I don't think it's a good idea to add more words to the naming of the profile.
The word magnetosphere is a term not really used for stars and the Sun, but for planets and moons. One can use the magnetic field in the solar corona as the alternative term, which is wordy to be used in a name.

Speaking of wordy. Mission panel info: Ylva has good points about simplifying the language. At the same time, I've written it in a way where I'm saying what content is there and how to use it. Ylva makes a great point about instead focusing on what the content is telling us " What are the fieldlines? What do they show? What do the colors mean? What do the colors on the sun mean? Why should we care about these things? How do they affect us? Etc. " To add this but at the same time keep it short is tricky and I'd appreciate help with it.
And a comment about the audience for this. Ylva also points out "The target audience seemed to be someone who is already familiar with the models." And I would say that that is correct. This is different from a lot of other content in OpenSpace in that way. I've made this in expectation that experts will be using it. However, I agree. It should be more accessible and a lot can be moved to the documentation page instead.

Also on the topic of the mission panel. Using the mile stones. I've thought about this too and I've wanted to add periods where there were CMEs but I recently learned that WSA is not modeling the CMEs but only the ambient background. I also have been wanting to put the end time to be todays date every day, but I believe in LUA we've blocked the use of the system functions for security reasons, which unfortunately is where getting the time lives. If anyone have a work around on that I'd love to add it.

talk about wordy...

I think the scale of the fieldlines is fine, it's just the max value that seems very low compared the scale they actually have. So maybe change the max value of the property, if possible?

If you want help to come up with some text for the mission panel, I'm happy to chip in! Chat gpt could also be a good tool for rephrasing things.

Here are the videos that became 404:
https://github.com/user-attachments/assets/598a92b3-c27d-4dfb-9129-5627a78e6a06

@ElonOlsson : To get the current time you can use openspace.time.currentWallTime()
@ylvaselling The Scale i believe is for the StaticScale, so we currently don't have the option to change the max value until #1529 is fixed