Even if you put Windows first in the BIOS, grub might get deleted. You might need to reinstall Grub. Hate to be morbid, but it's best to be prepared for that. If you happen to have Windows on disk 1, and linux including grub on disk 2, then you are much more immune to grub-killing updates, because in that setup, Windows can do whatever it wants to its own disk without affecting grub.
For some reason now when I start my Win10 + Solus Plasma dual-boot machine I only have a choice of either OS. I used to have an option for 'Advanced' * start for Solus but that option has gone. I don't know if it is related to either Windows or Solus updates or not. Does it matter I don't have that option now? The machine still boots into what ever OS I choose. Thanks. Edit: * It may have been 'Alternative' start option.
Maybe the new kernel removed the old one? https://discuss.getsol.us/d/3777-grub-alternative-boot-options-missing Anyway, I won't lose sleep over it.