DOMimages Sorry, for the lack of response for so long - personal stuff - though finally I'm getting back on track. So let me consider all your requests, one at a time with small breaks.
For that purpose, you can use a point as a domain and you'll be given a thing called "pivot point" and you'll be able to edit it as you like. If this is in the middle of the existing distribution I would suggest making exclusion scope in that place for eg simple rectangle/circle will be enough and adding an ecosystem with points as domains only in order to have the ability to edit those as you like.
Selecting the exact piece out of millions can be very tricky and would bring huge drawbacks to performance and memory handling. I would rather prefer to avoid that, especially since there is already a friendly way to achieve the desired result.