The internal changes to eggPlant in V12 were more fundamental than it might appear, so we can’t just add a switch you could throw to have it go back to working like V11. However, there may be things we could do to help satisfy your need if you can be more specific about what exactly you are looking for.
For example, if what you want is to have each script open in a different window, you can basically achieve that now (with a certain amount of effort on your part) by dragging each new script tab out to create a new window, and possibly collapsing the left-side lists. Those two capabilities in V12 (dragging tabs out to make new windows, and collapsing the left side) allow you to create a set of windows similar to what you had in V11. Since that capability exists, it might be possible for us to add an “open scripts in new windows” switch to save you the trouble of dragging tabs out by hand.
Please understand that’s just a theoretical example, not an offer to provide such a feature. But we are always interested in hearing what our customers need, so if you can be clear and specific about what you want we will definitely take those feature requests into consideration as we work on future enhancements.