That Mac supports:
Dual/Mirroring* 2nd Max. Resolution: 3840x2160 (4K)*
Details:* Although Apple originally only reported that this model could support a single external display up to 2560x1600, third-parties discovered that it actually could support a 3840x2160 (4K) display, and Apple subsequently revised their official documentation to confirm this, as well.
from:
https://everymac.com/systems/apple/macbook-air/specs/macbook-air-core-i5-1.8-13-2017-specs.html
Your computer supports ONE additional hardware-accelerated external display. That really suggest that if you want to support more displays, you may need more computer.
There are ways to support more external displays using more complex and expensive Docks and DisplayLink software, but they will not be hardware accelerated, and not suitable for full motion Video, gaming, and possibly not for mouse-tracking on that display.