Modifying unbuilt designs

[lavaflow]

Is there a way to modify a design before you build it other than the popup when it's finished the design process? I want to wait a bit before I actually built these new CVs of mine (budget concerns, it turns out 44kt BCs with 6x20" guns in 1926 are expensive... who knew?), so it's likely I'll want to update the design with new tech. However, I can't figure out a way to get the "modified from design 10/20%" so that I'd actually be updating the existing design instead of making a new one completely. Opening the design from the file in the designer doesn't do it.
I actually did test starting construction of one, from which I could open design and get the modifier/whatever it's called, but I can't save it because there's one in construction and if I try to cancel the construction the design window automatically closes.

[seawolf]

Build it, open the design, change the name and resale it, then cancel the original construction

[lavaflow]

That is is the obvious workaround, isn't it. Should've thought of that myself. Still, it feels like there should be a better way.