yes, of course ... If I try to update 'Spam' filter rule, it doesn't work ...

This doesn't magically fix existing filter scripts. You need to update 
or re-create that rule, and save the script again.

I'm sorry but problems are still there:

# Spam Filter
if allof ( not header :comparator "i;ascii-casemap" :contains "X-Spam" 
"-", header :value "ge" :comparator "i;ascii-numeric" "X-Spam" ["5"] ) {
      fileinto "Select target folder:";
      stop;
  }

and

# Spam Filter
  if allof ( not header :comparator "i;ascii-casemap" :contains 
"X-Spam" "-", header :value "ge" :comparator "i;ascii-numeric" 
"X-Spam" ["5"] ) {
      fileinto "Create new folder [pluto]";
      stop;
  }

Changes have been made in Git for this ticket:

Bug #10282: Additional fixes when creating new mailboxes

  3 files changed, 12 insertions(+), 12 deletions(-)
http://git.horde.org/horde-git/-/commit/b6426954c719dd09015c1d024920dec1a03f294d

Create new folder still does't work on 'Spam' rule; if I select 
'Create new folder', java pop-up appears, I enter 'minni' as new 
folder name, but after press 'Save', rule is saved on my managesieve 
server in this way:

# Spam Filter
  if allof ( not header :comparator "i;ascii-casemap" :contains 
"X-Spam" "-", header :value "ge" :comparator "i;ascii-numeric" 
"X-Spam" ["5"] ) {
      fileinto "Create new folder [minni]";
     stop;
  }

this appends ONLY on 'Spam' rule, 'Blacklist' and 'New Rule' work well ...

Similar problem, if I don't select any folder and leave selection on 
'Select target folder:'; if I press save button (on 'Blacklist', 
'Spam' and 'New Rule') rule is saved in this way:

# Blacklisted Addresses
if address :all :comparator "i;ascii-casemap" :is ["From", "Sender", 
"Resent-From"] "pippo@pluto.com"  {
      fileinto "Select target folder:";
      stop;
  }

  # test 3
  if address :all :comparator "i;ascii-casemap" :contains "To" "pippo"  {
      fileinto "Select target folder:";
      stop;

Changes have been made in Git for this ticket:

Bug #10282: Fix creating new mailbox in Ingo

  4 files changed, 12 insertions(+), 11 deletions(-)
http://git.horde.org/horde-git/-/commit/768fb076fc354ed40e83e979af981fa63476b166

I believe I fixed the issue.  Attached a patch against git master.

For example, I create a new filter rule as follows:

Rule name: Test rule
Subject contains: test
Deliver to folder...
I select the "Create new folder" option from the select menu, and I 
get a Javascript popup asking for the new folder name.  I input the 
name "test" (without the quotes), and the select menu updates to read 
"Create new folder [test]".

However, the "test" folder is never created.  If I look at the Sieve 
script that was uploaded to the server, the rule reads

fileinto "Create new folder [test]";

My server setup is as follows:


My server setup is as follows:

CentOS 5.6 x86_64
Apache 2.2.3 installed via yum from CentOS repo
PHP 5.3.3 installed via yum from CentOS repo
Horde 4.0.6 installed via Pear
Ingo 2.0.2 installed via Pear. Backend: sieve with timsieved (Dovecot 
Pigeonhole)
Net_Sieve 1.3.0 installed via Pear
Dovecot 2.0.13 installed from source
Dovecot Pigeonhole 0.2.3 installed from source

A few extra data points:

  - I have no trouble creating new folders via IMAP in Imp or from 
another IMAP client.
  - Pigeonhole is configured with "sieve_extensions = +notify 
+imapflags", the rest of the config is default.