[djmakinera]

filename & packagename search
[АA]\u

Unicode and normal letter.
Find only Uppercase.

[Jiaz]

Pattern is invalid

[Jiaz]

You can check pattern in regex101 and it will tell you where the error is

[djmakinera]

Now good.

^[AА]

But I do not know how to use the operator \u or \l

[Jiaz]

regular-expressions.info/unicode.html

[djmakinera]

I use \x{xxxx} for unicode code points
[\x{0419}\x{0041}]

CYRYLIC CAPITAL LETTER A
LATIN CAPITAL LETTER A

But it does not work properly, only for uppercase letters. Where did I make a mistake?

[Jiaz]

Either you have to specify the lowercase unicode point as well or enable
(?i) - case insensitive
and
(?u), Unicode case
see
docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html#CASE_INSENSITIVE

[djmakinera]

An option would be useful, for simplicity as in most Text Editor it has:

Enabled/Disabled
Case Sensitive
-or-
Match Case

[Jiaz]

I'm sorry but when working with regex, you should also know about modifiers and how to use them.
also with checkbox you will break modifiers because you can enable/disable modifiers multiple times in a pattern. Something you can't do with a simple single checkbox