Only thing to correct is your understanding of how customizing toolbars works in SketchUp.
On Windows there is no “Customize tab” for toolbars and there’s not supposed to be a “+” displayed on any of the toolbars. With View Toolbars open you can modify native toolbars by dragging tools to or from them. You can also create new toolbars and drag native tools to them if you want.
I wonder where you got the idea there would be a Customize tab or a “+”.
Make sure the toolbar you want to customize is displayed. When you select View > Toolbars, a check mark appears next to each displayed toolbar. If a toolbar isn’t displayed, select its name to display it.
From the menu bar, select View > Toolbars > Customize. Or click the Toolbar Options drop-down menu (the down arrow at the end of each toolbar) and select Add or Remove Buttons > Customize. Either way, the Customize dialog box appears.
Click the Commands tab, which displays a list of tools that you can add to a toolbar, as shown in the following figure. If you want to remove or move a tool, skip to Step 4.
(Optional) By default, the All Commands option is selected in the Categories list. However, you can narrow down the tools displayed in the Commands list by selecting a category in the Categories list. For example, select Arrange in the Categories list to display only the arranging commands in the Commands list.
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