On the entry field for Additional Boards Manager URLs is to small to use in rc4 and rc5. rc3 was OK. **To Reproduce** Steps to reproduce the behavior: 1. Go to 'File' 2. Click on 'Preferences' 3. Click on 'Additional boards manager URLs' edit Icon. 4. See error **Screenshots**  **Desktop (please complete the following information):** - OS: Linux Mint (Ubuntu) - Version: Linux Mint 20.3 Cinnamon