Startup Manager broken
I've installed Windows using Bootcamp utility.
I created a partition on the SSD and installed Windows on it.
after a while I started to run out of space on the Windows partition, but no way to extend that Windows partition. so i created a second partition and formated that partition also as NTFS
eerything worked fine. when starting up the macbook pro I hold down the option key where I can select to boot to Windows or Mac OS.
then I used a program while running Windows to migrate the two partitions together.
I realy tought to be sure it had nothing to to with the Macintosh HD partition.
but when restarting my machine I was not able to boot to Mac anymore.
MacBook Pro 15", macOS 10.15