Change different variables to the same name(manual variable merging)

[ret2ddme]

Is your feature request related to a problem? Please describe.
Take IDA, for example.

In some re challenge, there are to many variables named vxx, but in fact they are the same one.

Because the variable operation after disassembly appears as assignment between many registers or others. The IDA can't recognize that they're the same variable (The file has removed the symbol table).

IDA name them different variables just to be safe.

At the same time, IDA doesn't support name them the same name, so, it give me a hard time when the input data is heavily processed, the input string can be named in dozen different names.

[Escapingbug]

This should be related to manual variable merging. Thus I have modified the title to be more specific.

The underlining problem is that currently both IDA and ghidra does not support manual merging of variables. I will do more research to see the specific reason of this.