Where does the Grub go when selecting erase drive?

[BluishHumility]

@thunderstorm2kN

So you mean the second opinion aka :“Replace a partition”

No, I mean the last option: “Manual partitioning”.

Before you do that, close out of the installer and boot into Windows to resize the Windows partition. Do not attempt to resize the Windows partition from within Calamares.

@TilliDie

I would back your data up before you mess with things

This is very good advice.