It is not a bug. If you want the HTML bar appear every time you start EmEditor, please check “Automatically display the HTML Bar for selected configurations” check box, and check all configurations applied.
If you right-click on the HTML Bar button on the Plug-ins toolbar, a context menu will appear. At the bottom of this menu, you will see “Properties”. Please click on this.
Right-CLick on your MAIN toolbar,
Choose Customize Plugins…
Which is an oddity I think), since one would keep looking for it on Customize toolbars.
And you can’t get there by right-clicking on the HTML toolbar itself?