Of course the interface should eventually allow this to be pulled anywhere, or indeed to be turned off completely - as should be the case for any of the various viewers. I would allow a whole host of tools to share this work area. This would include assistants to check on te model and raise modelling issues to be addresses. An Issue handler or conflict resolving assistant. Tools to amend any Grammar or Lexicon and to check the impact on the model of any such change - again raising modelling issues if there are problems in the change.
Many aspects are user configurable.
The user should be able to move the boundary between any window panes to give more or less screen real estate to the views they are workign on or prefer. A set of initial layouts would be provided - a standard one would allow for egeneral use. Specilaised layouts for editing focuissed on some specific areas culd be provided - such as a layout that is better for acrtivity eiting, or a layout for global constraint editing, or one that is better for manipulating the grammars and lexicons, etc. However, I have not thought a lot about this yet. The editor should be able to store and load domain models from persistent repositories of various kinds.