With appropriate Role Security, you can use Custom Office to hide the button.  If you have the role option to allow accessing Custom Office via the CTRL+F9 hotkey, the easiest way to do this is to launch the task, click on the tab where the control is, then hit CTRL+F9 on your keyboard, you will likely want to set up this customization for all users and either specific companies or all companies. 

Once you have the panel open in Customizer, you can right click the control and then go to the "options" tab and check the "Hidden" option.  Click OK, then click the save icon or "Panel" > "Save".

However, a user specific customization will take precedence over the "all" users customization.

If you have a bunch of user specific customizations, you will need to hide the button on each one. 

An alternative route is to use a UI Post-Load event script on the pHeader panel to hide the button.  You can do this conditionally by company code or even whether or not a users as a specific role assigned.  If you use a script, the "Allow External Access" in Company Maintenance must be checked for each company the script needs to run under.

Thank you David. This was exactly what I needed and it worked perfectly.

Thanks for the hotkey trick. If I just want to play with customizer can I reset back to factory defaults or delete my changes?

Customizer creates a folder structure under the MAS90\XX folder where XX is the module code.  The first level is Custom.  The next level is the XXX-XXX where the first 3 Xs are the user code or ### for all users and the last 3 Xs are the company code or ### for all companies.  Within this folder will be a copy of the library file which is uses the .M4L extension.  So you aren't actually modify the stock libraries.  If you no longer want to use your customized library, you can either delete the dMain panel through Customizer Selection or rename, delete, or move the folders/files under MAS90\XX\Custom and then run the Rebuild Customizer Log task (not required but cleans up the list of "Customized Tasks" under Customizer Selection).  User specific and company specific customizations take precedence over All users or All companies customizations.

Thanks David for the detail use and cleanup of the customizer.