Yes, you would probably need a rule for unnested and a rule for nested.

I would satisfy the nested scenario with advanced F&R by having:
in template rule
Find = ({{foobar[^}]+)X
Replace = $1Y
regex enabled for Find

By setting ({{foobar[^}]+) or similar you will ensure that only the nested template is matched, actual level of nesting should not matter.

@Rjwilmsi, Yes, but that only works as a straight up find/replace. You can't use that with advanced options and skip conditions.

@Headbomb The example I gave worked for me, on the basis of having one rule for unnested cases, and the second rule with the details provided for nested template cases. Or is your actual need more complex than the example I provide, such that it doesn't work for another reason?

Oh I've got quite complex examples. For instance, I have this "accessdate remover" logic, that removes the access date of citations without urls.

In:

citation/cite book/cite journal/vancite journal/vcite journal

Find:

\|(\s*)access(-?)date(\s*)=(\s*)([^(\||\})]*)

Replace:

|$1access$2date$3=$4

Not contains:

\s*((chapter|contribution)-?)?url\s*=\s*(\/\/|http|ftp|\{\{)

Now if want to run that, and the citation is nested in an infobox, then I could sort of (lazily) modify the logic to have

In

citation/cite book/cite journal/cite web/ vancite journal/vcite journal/infobox foobar

However, it's possible infobox foobar contains a |url= parameter, and the skip conditions are all messed up. Or if another template in that infobox has an accessdate (e.g. {{cite simbad}}), then it could have its accessdate removed.

As I said, you'd need two rules:

unnested
Make the contains:
^(citation|cite book|cite journal|vancite journal|vcite journal)

So you only match unnnested. Rest should be the same.

Nested:

Contains:
{{(citation|cite book|cite journal|vancite journal|vcite journal)

Not contains:
{{(citation|cite book|cite journal|vancite journal|vcite journal)[^{}]+\s*((chapter|contribution)-?)?url\s*=\s*(\/\/|http|ftp|\{\{)

Find:
({{(?:citation|cite book|cite journal|vancite journal|vcite journal)[^{}]+\|\s*)access(-?)date(\s*)=(\s*)([^(\||\})]*)

Replace:
as currently.

However, if an infobox has two citation templates in it, or the citation template itself has a nested template, you won't handle everything. A simple custom module would avoid all of the nesting issues:

...
ArticleText = Tools.NestedTemplateRegex(new List<string>("citation/cite book/cite journal/vancite journal/vcite journal".Split('/'))).Replace(ArticleText, m => {

string templateCall = m.Value;

if(
  Tools.GetTemplateParameterValue(templateCall, "contribution-url").Length == 0 &&
  Tools.GetTemplateParameterValue(templateCall, "contributionurl").Length == 0 &&
  Tools.GetTemplateParameterValue(templateCall, "chapter-url").Length == 0 &&
  Tools.GetTemplateParameterValue(templateCall, "chapterurl").Length == 0 &&
  Tools.GetTemplateParameterValue(templateCall, "URL").Length == 0 &&
  Tools.GetTemplateParameterValue(templateCall, "url").Length == 0
)
{
  // UpdateTemplateParameterValue will only change parameter value if it already exists
  Tools.UpdateTemplateParameterValue(templateCall, "accessdate", "");
  Tools.UpdateTemplateParameterValue(templateCall, "access-date", "");
}

 return templateCall;
});
...

I don't know how to use modules, I don't know what that coding language is, I have like 40 "In Cite xxx" subrules (and the one presented above has been simplified for sake of clarity), and I'd need to add 200-300 "In: <Infobox>" logic, on top of any other templates that may have a citation nested within it.

Why can't AWB just get that "Look at the deepest level of nesting" option? This way *everyone* can do this properly with minimal effort?

@Rjwilmsi is there a regression here? The latest version seems to not do this anymore.

Going to ping @Reedy too on this.

@Headbomb what's your test case/example that used to work and now doesn't?

@Rjwilmsi
Well if you have something like

In template call -- > Cite web -- > Find JPL --> Replace with nothing

and run it on [https://en.wikipedia.org/w/index.php?title=User:Headbomb/Sandbox&oldid=877842965 you get nothing.

But if you run it on https://en.wikipedia.org/w/index.php?title=User:Headbomb/Sandbox&oldid=877843062 you get something