10 Curves

[Thommy7571]

I tried to digitize 10 straight lines, which is usual for certain kinetic technics in chemistry.
Why can I only select the 5.curve but not the following? - The box
to choose, the curve stays grey.
I can add more, but I cannot select them in the box...

Can you add the possibility to select and digitize about 20 curves?

Thanks

Thommy7571