in Markush patent structures often zero "repeating units" (or zero "link atoms") occur.
In the attachment the problem is illustrated by an example and the enumerated result.
How can a Markush structure with zero repeating units be defined in Marvin without opening up the ring system during enumeration of the structures?
You are right, zero repetition is not yet supported and ideally the enumeration should not break the ring.
We will look into this. I think that the enumeration will be easy to fix, but chemical registration and searching will take time.
In the meantime, I suggest to use an R-atom in place of the repeating unit, as in the attached Markush structure. It is important that the attachment points are added in the appropriate order for the R-group definition.