One way to fix it is by using Ventoy and adding a rEFind CD-R image file to the ISOs’ folder. Then select your Ventoy media with F12 to boot into the reFInd live ISO and upon the main menu, choose Windows next. From there, on Windows, you can do a system repair or a reset. Remember to remove your USB with Manjaro.
Alternatively, you can download a Windows ISO and boot from it with Ventoy or directly by burning an ISO to a fresh drive. Once it boots, choose recovery environment to perform a boot/system repair. If I recall correctly, this is the only viable way if BitLocker is enabled.
In some PCs and desktops, you can just enter the firmware settings and locate the boot options page and set the Windows bootloader to run first. You may need to turn on secure boot. In some computers, due to firmware restrictions, you’ll need to do that from your Manjaro USB.