Does installing GRUB to 2nd SSD does harm to Windows bootloader?

I mean when i get rid of the 2nd SSD. Can i boot to windows normally?

So … if you have a windows box that boots off it’s primary disk, but has a secondary disk, write a GRUB boot sector to a secondary disk, then remove that secondary disk, I would expect the machine to boot windows normally. The ‘what if’ issue you have is, what if there is a mistake somewhere along the line and the new boot-loader is written to the primary windows disk. In this instance, you have a problem.

Personally I would physically disconnect the primary windows disk before attempting to write a boot-loader on a second disk, mainly because (a) I’m paranoid and (b) the last windows laptop I had didn’t come with any (re-)installation media (!)

Also, be sure you “know” which disk the current Windows boot-loader is written to, your concept of primary / secondary might not match with where it has actually stored it’s “stuff”. (i.e. disconnect what you think is the secondary disk and make sure it still boots!)