Move the numeric_collation tweak to global preferences with the UI in Preferences / Behaviour. I didn't put it in db.prefs because I didn't want to create a linkage between icu.py and the database.

resources/default_tweaks.py

@@ -541,13 +541,6 @@ preselect_first_completion = False
 # Asimov and Quasimodo, whereas the default behavior would match only Asimov.
 completion_mode = 'prefix'
 
-#: Recognize numbers inside text when sorting
-# This means that when sorting on text fields like title the text "Book 2"
-# will sort before the text "Book 100". If you want this behavior, set
-# numeric_collation = True note that doing so will cause problems with text
-# that starts with numbers and is a little slower.
-numeric_collation = False
-
 #: Sort the list of libraries alphabetically
 # The list of libraries in the Copy to library and Quick switch menus are
 # normally sorted by most used. However, if there are more than a certain

src/calibre/db/categories.py

@@ -11,7 +11,7 @@ from functools import partial
 from polyglot.builtins import iteritems, native_string_type
 
 from calibre.ebooks.metadata import author_to_author_sort
-from calibre.utils.config_base import tweaks
+from calibre.utils.config_base import tweaks, prefs
 from calibre.utils.icu import sort_key, collation_order
 
 CATEGORY_SORTS = ('name', 'popularity', 'rating')  # This has to be a tuple not a set
@@ -115,7 +115,7 @@ def clean_user_categories(dbcache):
     return new_cats
 
 
-numeric_collation = tweaks['numeric_collation']
+numeric_collation = prefs['numeric_collation']
 
 
 def first_digit(x):

src/calibre/gui2/preferences/behavior.py

@@ -76,6 +76,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
             signal.connect(self.internally_viewed_formats_changed)
 
         r('bools_are_tristate', db.prefs, restart_required=True)
+        r('numeric_collation', prefs, restart_required=True)
         r = self.register
         choices = [(_('Default'), 'default'), (_('Compact Metadata'), 'alt1'),
                    (_('All on 1 tab'), 'alt2')]

src/calibre/gui2/preferences/behavior.ui

@@ -208,6 +208,20 @@ If not checked, the values can be Yes or No.</string>
       </widget>
      </item>
      <item row="1" column="0" colspan="2">
+      <widget class="QCheckBox" name="opt_numeric_collation">
+       <property name="text">
+        <string>Recognize numbers inside text when sorting (needs restart)</string>
+       </property>
+       <property name="toolTip">
+        <string>&lt;p&gt;Setting this means that when sorting on text fields
+like title the text "Book 2" will sort before the text "Book 100".
+Note that setting this can cause problems with text that starts
+with numbers and is a little slower. This setting is per user, not
+per library.&lt;/p&gt;</string>
+       </property>
+      </widget>
+     </item>
+     <item row="2" column="0" colspan="2">
       <widget class="QCheckBox" name="opt_delete_news_from_library_on_upload">
        <property name="text">
         <string>&amp;Delete news from library when it is automatically sent to reader</string>

src/calibre/utils/config_base.py

@@ -542,6 +542,12 @@ def create_global_prefs(conf_obj=None):
                    'on case-sensitive searching'))
     c.add_opt('case_sensitive', default=False, help=_(
         'Make searches case-sensitive'))
+    c.add_opt('numeric_collation', default=False,
+            help=_('Recognize numbers inside text when sorting. Setting this '
+                   'means that when sorting on text fields like title the text "Book 2"'
+                   'will sort before the text "Book 100". Note that setting this '
+                   'can cause problems with text that starts with numbers and is '
+                   'a little slower.'))
 
     c.add_opt('migrated', default=False, help='For Internal use. Don\'t modify.')
     return c
@@ -650,6 +656,18 @@ def read_tweaks():
 tweaks = read_tweaks()
 
 
+def migrate_tweaks_to_prefs():
+    # This must happen after the tweaks are loaded
+    # Migrate the numeric_collation tweak
+    if 'numeric_collation' in tweaks:
+        prefs['numeric_collation'] = tweaks.get('numeric_collation', False)
+        tweaks.pop('numeric_collation')
+        write_custom_tweaks(tweaks)
+
+
+migrate_tweaks_to_prefs()
+
+
 def reset_tweaks_to_default():
     default_tweaks = exec_tweaks(default_tweaks_raw())
     tweaks.clear()

src/calibre/utils/icu.py

@@ -9,7 +9,7 @@ __docformat__ = 'restructuredtext en'
 import codecs
 import sys
 
-from calibre.utils.config_base import tweaks
+from calibre.utils.config_base import tweaks, prefs
 from calibre_extensions import icu as _icu
 from polyglot.builtins import cmp
 
@@ -87,7 +87,7 @@ def sort_collator():
     if _sort_collator is None:
         _sort_collator = collator().clone()
         _sort_collator.strength = _icu.UCOL_SECONDARY
-        _sort_collator.numeric = tweaks['numeric_collation']
+        _sort_collator.numeric = prefs['numeric_collation']
     return _sort_collator