Legacy Adobe Analytics (<=H26) has variables for dynamically populating s_account:
For some reason this was removed from the new AppMeasurement library. These are incredibly useful variables used by many people.
Currently DTM encourages you to use the AppMeasurement library and I have a feeling when Adobe eventually fully integrates the core lib into DTM, they are only going to use AppMeasurement instead allowing option for Legacy. In either case, currently DTM only allows you to specify a live vs. staging s_account value, and the only way that gets populated is if you include the specific script URL for the environment, or use the _satellite methods for changing the environment. This is not at all the same principle as the dynamicXXX vars.
What I would like to see integrated into DTM is the same functionality that dynamicXXX vars offer. There are of course ways to override things with custom code, but I would like to have it integrated as part of the DTM tool, since the major selling point of a tag manager is to minimize custom coding.