you have had solus for about a week so nuke it, you don't have it where you want it yet or anything important saved.
I would install WIN. Use their dskmgmt.msc (is that right?) after install, and make a partition for Linux the way WIN wants you to make a partition for Linux. Then go live and install Solus in the partition you made with WIN.
I did it exactly this way for a bare metal "hop" distro and WIN accepted the distro's bootloader and I could pick on install. I was shocked it worked. It was 3-4 years ago but I doubt WIN instructions have changed.
I've never seen life this easy when the sequence is reversed personally....but many here do what you describe regularly so consider all opinions. 2 cents edit/clarity. I hope. and typo