Dear 1as
As Tajsateesh has pointed out, one should not post multiple identical threads. I have merged the threads so that members, including you, can view and respond to the query at one place.
Coming to your query; the designation with which you were appointed is what is to be considered for 'establishment matters' purposes. Which means that your salary slip, promotion/incentive letters, memos etc. will be issued in your name with this designation.
The nature of work may vary from time to time, depending on the exigencies; and this should not affect the designation.
However, since you say you have been TRANSFERRED. Now, is this transfer formal - with a formal transfer order; or you were simply directed to report to the Hardware section ??
What does the Transfer Letter mention your designation as ??
As already given earlier, the situation is flexible: for the purpose of an experience letter.
The usual format of which can be as below :
"Mr. ABC joined XYZ Co. as ..... Software Engineer on ........ During his tenure he has worked in Hardware Division......... etc etc. "
Warm regards.