You can use KISSoft (https://www.kisssoft.com/en/academy/events/gearbox-design-and-analysis), it a paid software. This software will be really useful for designing gear based on requirements and most advanced software I have seen.

But if you are hoping for free then download MITCalc (https://www.mitcalc.com) (demo version has all features), it is based on excel sheet and you can manipulate data and after that when you couple the MIT calc with solidedge or other compatible software it will export the design in 3D or 2D CAD data.

My experience: I used MITCalc coupled with solidedge to get all gears I want form bevel to helical gear. After the gear design, with subsequent knowledge you can design gearbox as per your wish. Here is the model I used the above said methods: Grundfos Gear Challenge