Windows’ boot loader doesn’t support other OSes. Linux install its own boot loader called Grub and it can be used for booting Linux and Windows. However, if you want to cleanly remove Linux, the best case is to have GPT partition table and install in UEFI mode. If your computer is older, you may however be having MBR (dos) partition table and legacy boot, which I know less so other should speak about it.
For testing purposes I would suggest different solution thou. Take 2 USBs, one of them, where you install Manjaro, should be USB 3. Create bootable live is on some other USB, then install it with boot loader on this USB 3. Then set in BIOS to have it as first boot. This way, whenever you put your Manjaro USB, you will see Manjaro Grub (boot loader), but when you remove USB, Windows will start normally. So your system and computer disc will be intact. You must be careful thou and point to the better (USB 3) as your Manjaro install destination along with boot loader. If you choose your hard drive by mistake… However, if you choose empty USB, you will see option to install Manjaro. If you point it to computer drive with windows, you will see other options, like installation alongside windows.
P.S. Always when messing with systems, do a system and files backup! In case of windows, create also recovery and install DVD’s just in case.