Awesome, thank you @TenPatrol ! I have updated the first post with it.
Just for the record this is the SDK solution:
1.1. Install, preferably on you SSD, it’s only 2.4GB, “Microsoft flight Simulator 2020 SDK” as explained on this page:
MSFS2020 SDK is here – Start developing FS2020 Add-ons! – Microsoft FS2020 – SurClaro
1.2. Launch the game using the program:
“Your MSFS SDK install folder”\Tools\bin\fsdevmodelauncher.exe
Can you describe “very fast” please.
AS a developer myself, I can say there are many good reasons to access these two files during startup. Mostly housekeeping and updates. Note I am not from Asobo or Microsoft, so i can only speclater, based on observation, and experience.
Firstly, during startup, MSFS checks for new content. As such this si a good opportunity to update the Manual Cache if needed (or at the very least mark as updatable). This is probably what people would expect as a functionality of a manual cache, an area that is always on local storage and should not need to downlod new data on the fly.
The same thing applies to the rolling cache. Whilstr I am not sure if it actually updates the cache (I doubt it) it may instead use this opportunity to invalidate old areas (and areas that have been updated) as this is not an insignificant process. as well as any other garbage collection. Also remember at this point you MAY have added community content, which may have an effect ont he manual cache/rolling cache, so that would need to be processed too.
I personally keep my FS installation on my main NVME (1TB) and all my addon content on a second 2TB Evo ssd on SATA, linking the folders into my community folders as needed, using MSFS Addons Linker to keep it simple.
I have also done something that I REALLY dont reccommend to anyone, but i have turned off the Windows defender AV on the MSFS folder (not the add-on folder). This does improve the perfromance under certain situations for me, but I REALLY dont reccommend it. Seriously dont do this, unless you are willing to take a huge risk, and dont blame me or MS/ASobo if somethign goes wrong, i really mean it, the risk is quite high especially with add on content, and the fact even add on content can have executable files (I have not prevented the add-on folder from checks)
Here’s an icon you can use for your new CMD shortcut (it works in Win11 so should work in 10 too). I can’t upload the format but it can easily be opened and then exported as a .ico file in Gimp.
The check for updates only seems to happen after the splash screens but I guess there’s nothing wrong with occasionally using the original link to be sure.
Here is a utility I found out about on the DCS forums. It worked well for me.
FolderChangesView - Monitor folder/drive/files changes on Windows
FolderChangesView v2.32
Monitor files changes on Windows
Copyright (c) 2012 - 2020 Nir Sofer
Description:
FolderChangesView is a simple tool that monitors the folder or disk drive that you choose and lists every filename that is being modified, created, or deleted while the folder is being monitored.
Link to the DCS thread:
Go to:
C:\Program Files\WindowsApps\Microsoft.FlightSimulator_1.17.3.0_x64__8wekyb3d8bbwe
Open file named Logo.png or StoreLogo.png and save as .ico
Thanks, I actually looked for that in my local files, I guess now I have a choice.
Thank you for the windows defender trick. I have added it in the solution as a link to your post with a warning “DANGEROUS, DON’T USE IT”. And… I did use it 
I respectfully disagree with your statement about updates though: updates, including content and cache, should be managed separately imho, either from the Microsoft store/steam, a proper separate executable launcher window, or from the menu of the game already loaded, with options to disable the automatic check for updates and to trigger the updates manually.
I have updated the first post with a batch file. The solution now moves to the SSD a total of 23.3GB, contained in 67 folders, which further improves loading times.
Thank you, I add it to the tools paragraph.
Awesome! I actually used this icon too.
Why does MSFS like to be on the boot drive?
I have MSFS installed on a second SSD on the D: drive. What advantage would I get from installing it on the boot drive? I will NOT be installing it in the App directory. I happen to be building a new computer as we speak, so this is perfect timing for this discussion.
On my current an new computers, I have two 1 TB SSD drives.
For the OP, I know this is off topic, if your motherboard doesn’t support a second M.2 slot, or it’s an old motherboard and takes up SATA slots you can’t give up, or is the single SATA line style, they make adapters that go in a PCIe 4 slot if you have an extra one, and they work great, often faster than dedicated M.2 slots on motherboards, which may only use a single SATA line, or other similar bottlenecks to SSD speed that a proper PCIe connection can eliminate.
Do you know if moving these files off my SSD to my HDD would reduce in game performance? Or just increase my loading times slightly?
Most probably because for the majority of people the boiot drive is the default, and usually the fastest drive (in fact most apps byu default install on your boot drive, and you haev to select otherwise)
Only depends on what type of drive and what type of data. For example, I have my MSFS installed on the boot as its NVME (not just for the transfer speed, but the high parrallelism NVMe provides) , but I have my community and third party content on a second SATA SSD to save some space, and linked it in.
Note, not all second NVMe slots are as perfromant as the first. For exampel on Ryzen CPUs the primary NVME is connected usually direct to the CPU on dedicated PCIe Lanes (not sure how it goes on intel) but the second one is connected through the chipset instead (where it shares lanes with other devices)
There may be some benefits for the installing on the boot drive in the future if Direct Storage can only work from the boot drive (or rather primary NVME, for the reason described above)
In my experience, installing content on HDD increases the loading time but doesn’t change the performances for which the main bottle neck is CPU 1 thread speed due to poor multithreading. Asobo claims multithreading this will be more optimized in a future update which should yield performance increase. Once the flight is loaded additional data comes either from internet or from your cache, it’s relatively low bandwidth, even for a HDD. On the contrary Star Citizen, for example, streams thousands of new objects per seconds and as a result installing Star Citizen on a HDD is completely game breaking because you may fall off in limbo from the hole of some missing asset that is taking too long to load due to the extremely high bandwidth needed.
Of course in your case, you should better keep these 67 folders on your SSD and move the rest on the content to your HDD, then you need to adapt the batch file in order to do folder junctions in your SSD with mklink command for those other folders pointing to your HDD.
Yeah my MSI B550M has two M.2 slots but only one of them is PCI-e 4.0
If someone can confirm all of this solution works for the Steam version, especially Step 2 making use of mklink folder junctions, that would be great.
You need a bigger boat😁. Don’t know what system you are using but you can get a 512mb 2280 NVME for $70 and either house internal or get an enclosure cheap. Either way, get a SSD just for the whole game, with some room to spare. Good luck
It’s certainly interesting. Currently I have a couple of folders on my desktop, one is a shortcut to the community folder and another I’ve labled community spares where I store any addons that I’m not using at the time. It is simple to swap them and it works but of course it is another task that needs to be done before flying and that eats some seconds even if my Pro Evo 980 is lightning fast.