If I change Parameter Variables under the Results-->Source Code tab in A Custom Project then those parameters are used in all the other custom projects and in builder.
I don't know if it's supposed to work that way or not?
However, if I then select Recommended parameters without unselecting any of the Your Own Settings from the Results-->Source Code tab it will include All the Parameters still selected under Your Own Settings.
I agree it doesn't seem to do this if saving from a Data bank.
Each source code type (MT4,5, TS) has its own separate setting.