Sometimes you really want to copy some model lines from a project RVT to a family RFA, but Revit says NO!
This is the workaround:
In the Project, create detail lines that describe the elements you want to copy
Make New Family – Generic Profile
Copy the detail lines in the Project (Ctrl + C)
Paste them into the Profile family (Ctrl + V)
Open / create the other family you want to put those lines into
Copy them from the Profile family into the other family (lets say it is a Planting family). They will appear as model lines in the Planting family. Yay!
Sure, this method has some limitations, but it is a valid workaround in a lot of situations.
Make sure you save before trying this… I did it in a fit of "ah-ha! Got you now Revit!!" glee… and the whole program shut down =(
if you convert your lines to model lines in the project environment you can then cut/paste straight into your generic family
If you convert your detail lines into model lines within the project you can cut/paste them straight into your generic family