The main steps are
- drawing of the single-line structure using full-parametric sketches replicated with arrays and mirrors and linked together
- automatic attach of steel beams over the centerlines
- adjustment of profiles rotation and offset of head and tail of beams, which is persistent even after modification of the underlying sketches
- creation of customized profiles based upon sketches
Though the "flamingo" workbench will have soon a quite drastic re-arrangement, this workflow seems very quick and flexible and I'll keep that also in future development.
If you have any improvement or integration with other features of FreeCAD, which I may not be aware of, please write suggestions in the thread of the workbench.