Is there a software to calculate parameters from certain inputs on a flying wing? I want to build something similar to this

https://www.parrot.com/de/drohnen/parrot-disco-fpv#parrot-disco-fpv-details

but with two holes in the wing, where I want to put two propellers. But I need to make the proper calculations (shape and size of the wings, I'll work on the propellers separately). It should be a simple design, just a prove of concept.

Is there a software that can help me do this? I can have an idea of the weight I need to lift, the velocity, and need the design (with the two holes).
Yeah you could start with X-plane, which claims that it can figure out the flight characteristics from geometry parameters. It is based on laminar flow theory and on classic aeroplane shapes and configurations, but it is a start. They have something called Plane Maker which could serve your application.

FlightGear is a similar program, open source so you can study the code to see how it works, then try to find relevant lift and drag data on the interwebs, NASA servers for instance.

Good luck with the modelling effort.