Highend menu conflict with “If Menu” plugin

I want to make the main header menu conditional using the “If Menu – Visibility control for Menu Items” plugin.

After installing and activating the plugin, then when you go to the menu configuration section I get the following message “If Menu detected a conflict with another plugin or theme (HB_Custom_Walker_Edit) and may not work as expected.“. Please see attached screen shot.

I have read the Plugin FAQ and I see this explanation:-

If Menu is broken, no visibility rules are available

There’s a known limitation with adding functionality for menu items in WordPress, and conflicts may happen between some plugins and themes.

If there are multiple plugins that extend Menu Items, for example If Menu and a plugin for Menu Icons, only one of them can add the needed functionality and the other one won’t work as expected.

This is an ongoing issue with WordPress which hopefully will be fixed in a future release.

If the “Menus” page is blank or options for visibility rules are not displaying, there is a way to test which plugin/theme causes this conflict.
Please disable other plugins or themes until you find the one that causes the problem, and contact the respective developers.
In the message include the link to WordPress ticket about menu items https://core.trac.wordpress.org/ticket/18584 where they can see detailed info on how to fix the problem.

Can the Highend theme (HB_Custom_Walker_Edit) be turned off to allow the If Menu to work or is it all or nothing?