A discussion elsewhere prompted me to check if there is a label reading the lenght of a line or a polyline. And it looks like it is not, and on top of that, you cannot ID or label a line or polyline.
Yes, there is a Travel Distance object that can be nicely reshaped and that shows its length in Imperial and metric, and can be tweaked... but that is thanks to the good will of the author of the Travel Distance object. There is also an addon at http://simpleaddon.com/Eng/td_product.html
So... more properties for the 2D elements? Lines, polylines, fills? Hm?
Or....GS could provide a polyline tool that will calculate segment lengths and overall lengths. Colleagues in the US doing commercial work need to calculate egress path lengths for most building permit submittals, along with building perimeters. I believe AutoDesk has provided this capability within their software. I'm by no stretch a software programmer, but it seems this would be low hanging fruit to add into Archicad - hopefully in AC26.