Okay. UltraEdit v15.00.0.1035 has multiple toolbar configuration files, 1 file for every environment. You can switch between the environments via View - Environments. All the configuration files for an environment are stored in the directory of the INI file currently used by UltraEdit. You can see the full path and file name of the INI in use at Advanced - Configuration - Application Layout - Advanced. The location depends on your operating system (version and language) and your Windows user account name. If you enter that path or %appdata%\IDMComp\UltraEdit\ in the file edit field in the file open dialog (Ctrl+O) and press key RETURN, you should see all the configuration files. *.tb1 are the text files containing the toolbars information. Open a file with extension tb1, insert a space, delete it with BACKSPACE and save it. If that works, the files are not write protected.
I suggest to customize the toolbars to what you like, then open View - Environments and press the button Save Current State As. Next select your environment. After exiting UltraEdit and restarting you should see your customized environment.
Best regards from Austria