Currently in VS if let's say I change the Set to a Dictionary it will compile in the background and then complain about all the errors from where I can click on them to be taken there, and/or I would search on the variable name and find all the references and just scan through all of them to make changes as necessary.

Some ideas there could be: a) We can use multiple windows (or lines in 1 window) to just quickly display all of the required changes directly on screen without me having to manually go from one to the next.

b) Let's say we were doing a standard List.Add but now its a Weird.Blob (ie. a non-standard class with no built in conversion support). I can perform a replace all .Add with .Blob which text editors can already do, but what if we only applied it to this current set of windows that have opened up, so as to not break other things? Again you could have done that with a narrower replace, but this way might be easier or faster.

c) In text editing you might have to replace a few lines several times, so you'd copy the new line or a segment of it, then replace all the parts of the old instances. What if we sorted all those opened windows so that the ones that are most similar are located next to each other, then if we change one we just drag it (or parts of it) to the other windows to make replacements. If they are exactly the same then provisionally change them automatically, the user just accepts the whole block of changes (as if they had done a search/replace for a specific line, or part of a line).