TAD (The Architect’s Desktop) was written by Sabu Francis (i.e. me) It started as a design system for architects; and especially covers the early stages of design. The avowed aim of that tool is to cover the entire range of the architecture life-cycle. However that grand goal has not yet been achieved.
Nevertheless, the aim of TAD is to actually reach AIM 
All my projects which I did at SFA (Sabu Francis & Associates) used TAD as the modelling system and we achieved fair amount of success. Our office was one of the main architects for Konkan Railway. We did all their architectural works, and that excluded the railway itself and the railway stations.
Those who are interested in TAD; you can register at www.teamtad.com and follow the registration instructions. TAD is free and will remain free.
Registration for TAD requires that you become a member of a Discord community specially setup for TAD (It’s called teamTAD community)
But you can choose to become the member of that community even if you do not want to use TAD. You can join the TAD Discord community using this link: https://tiny.cc/ttad
What is Discord?
It is a large system for making communities. Originally started for gamers; for them to gather together and chat (especially when playing the game); Discord is now a general purpose community system. Once you enroll into Discord, you can join other interesting communities there. Discord has excellent audio/video features and also screen-sharing. That was the reason why TAD community was setup on Discord; as help can be provided by video and screen-sharing.
Declaration: I; Sabu Francis, is one of the persons behind AIM and this forum too