Such values are nor recorded in files but in moodle database (mdl_config_plugins table).
If there is REALLY no save button on the page, the only solution is to change the value directly in the database. BE CAREFUL !!!
If you have a visual mysql editor, look for the line in that table where 'plugin' = 'theme_adaptable' and name = 'toolsmenu1' and delete/update the 'value' field.
Otherwise execute the following sql statement
SET value = ''
WHERE plugin = 'theme_adaptable'
AND name = 'toolsmenu1'
Hope it helps