After reopened "Preferences..." dialog custom tools are in "Supported tools"

Scenario.

1. Create custom tool
   1. Create file "CustomTool.xml" with the follow text

      <?xml version = "1.0" encoding = "UTF-8"?>
      <ugeneExternalToolConfig version = "1.0">
          <name>Custom tool name</name>
          <id>CUSTOM_TOOL_ID</id>
          <executableName>custom_tool.py</executableName>
      </ugeneExternalToolConfig>
      

   2. Open Settings->Preferences...->External Tools
   3. Click Import and select "CustomTool.xml"
   4. Click "OK"
2. Open Settings->Preferences...->External Tools again
   Expected state: custom tool "Custom tool name" will be in the "Custom tools" section