Right. Rules cannot have links to other rules. You have to do it as Entries. Possible to use minselections+maxSelections, but if you use a link to the container entry then you have to use an entry group to cause it to be pre-selected.
There are many rules like that. Not to mention all the profiles with links to Fleshbane, Melta, etc.
In my catalogs so far, I have to assume that everyone knows the rule for Twin-linked, Melta, Armourbane, Fleshbane, Pinning, and Master-Crafted or else I'd have to enter the entire base rulebook.
@efalsken for modifiers keying on entries that is fairly standard practice. (Painful but standard) But linking rules to other rules would allow easier "deep linking" to clarify interactions (at least in the rules section)
Though ... Being able to so a "if Rule X is applied, apply this modifier" would be rather useful
i'm of the opinion that I should not modify the base profile beyond changing unit type or adding an invul save. They don't stack well all the time (set-to vs add-to) and make it unclear which bonuses have been added to the base profile unless you also modify the name. And that gets just downright crazy with all the modifiers.