Q1)
When I use .replace and i don't want to replace the original string, do I need to make a copy of it? or is there an API that doesn't replace the original string?

example:

QString str = "a - b";
QString str2 =  str.replace(str, "-"); 

this will replace the content of str but I would like it to don't, do I need to make a copy before?

Q2)
I wonder if there's any API to count the number of replacements done on an str.replace?

I was reading the docs of replace but I didn't see any count parameter https://doc.qt.io/qt-6/qstring.html

Do I need to build mine or maybe use regex match and count the size of the match object?

Q3)
Is possible to check the substring without declaring a string before?

QString s = "...";
QString s2 = "100000";
s += s2.mid(0, 6 - (s.length() % 6));

to something like

QString s "...";
s += "100000".mid(0, 6 - (s.length() % 6));

Q4)
Is it possible to see the content of QRegularExpressionMatch match object in the debugger watch of Visual Studio? it only shows some pointers.