[OutputBuilder] Add new groups (created by clicking "Add"/"Copy" on existing group) to `groups` collection of RHS model.
[OutputBuilder] Add new groups (created by clicking "Add"/"Copy" on
existing group) to `groups` collection of RHS model.

Do this to prepare for implementing logic for updating group positions
after inserting/deleting groups.

itsjeyd/ODE,itsjeyd/ODE,itsjeyd/ODE,itsjeyd/ODE