Having trouble installing UE4, and getting the launcher to recognise an already-installed engine

I am trying to download UE4 to my Macbook, but I was initially hit with error code IS-DS01 for not enough space in the install location (even though I had about twice as much free as needed). As a workaround, I installed it to my removable drive, but this did not work as my drive is apparently case-sensitive. I copied the engine over to where it was originally supposed to be installed on my Mac drive, but the launcher only recognised the installation in the removable drive, even when I created a symlink from /Users/Shared/UnrealEngine to the new location. I deleted the launcher entirely and re-downloaded it, but now it does not recognise any installation, even the one on the removable drive that it previously recognised. I tried to follow the advice from this forum question:

to get the launcher to recognise the existing installation with a $movedMarker folder inside the /UE_4.27 folder, but when I ‘reinstall’ the engine in this /UE_4.27 folder I get the same IS-DS01 error. In writing this question I have noticed that I misread the advice from the above question, and that $movedMarker should be a file rather than a folder; however, the advice does not specify the necessary file type (it’s quite possible that this is obvious and I’m just dumb).

I am wondering how I can install UE4 (ideally without reinstalling the whole engine, but rather getting the launcher to recognise what is already installed). Perhaps I need a bit more guidance on the $movedMarker method, or even just a fix to what appears to be an incorrectly triggered IS-DS01 error in the first place. I would greatly appreciate any help.