. I believe more powerful Regex “flavors” do allow changing the capitalization of strings. I believe tokens \U and \L are allowed in more powerful Regex flavors, but not in .NET which is the one used by Trados, I believe.

It would be great and incredibly useful to allow Regex to manage capitalization changes.

Multiple situations where this could be useful:

1.- Change the first letter in every segment from uppercase to lowercase.

2.- Ensure each letter after a period is uppercase.

3.- Changing to lowercase in all letters in segments but the first.

While these situations where this could be useful are not commonplace in normal translations, they are very useful in sections where a lot of digits/letters or codes are used, or for correcting OCR transcriptions of large datasets. Another place where they are useful is when using machine translation; I have found that headings such as 

(a) This and that

(b) That and this

(c) This and this.

are very commonly machine translated as (A), (B) and (C). Changing a thousand of them is a big nuisance.

I can assure you, these situations arise more often than you could imagine, and as far as I know there is no way to solve them.