In the meantime, it should be possible to work with something a bit less flexible.
Following the spec you could add the name at the top of your feature, like this:
name "Extra Boring Sub";
sub B by B.ss03;
And then do the same thing within the Replace Feature custom parameter.
Sidenote: I am a bit confused about the usage of parantesis etc. in there. The syntax is not 100% the same as in the feature window. But why? Also look out for autocorrected quotation marks.
Remember that this workaround might cause problems if you have a name defined at the bottom of the feature window. So make sure to delete the info there before you try this.