@boddunan Can you try to re-procedure the issue with a Joomla core components which also uses Categories like com_content or com_contact ? We do not have access to your component, so it is hard for us to see the issue ourself to see what's wrong.

Also, in step 8 and step 9 which you described, normally, for core component, you will select a category from modal popup, not from a dropdown. Maybe that's the difference from how your component with core components.

@joomdonation the issue is only with the category form field. Since the article category blog uses modal dialog, I do not see this issue.

Could you please attach the default.xml of your category so that we know exactly how you use that field ? Or better, use modal to allow selecting category like how we are doing it in the code.

Please find it below.

<?xml version="1.0" encoding="utf-8"?>
<metadata>
   <layout title="COM_MYCOMPONENT_CATEGORY_VIEW_DEFAULT_TITLE" option="COM_MYCOMPONENT_CATEGORY_VIEW_DEFAULT_OPTION">
   	<help key="JHELP_MENUS_MENU_ITEM_CATEGORY_LIST" />
   	<message>
   		<![CDATA[COM_MYCOMPONENT_CATEGORY_VIEW_DEFAULT_DESC]]>
   	</message>
   </layout>

   <!-- Add fields to the request variables for the layout. -->
   <fields name="request">
   	<fieldset name="request">
   		<field name="id" type="category" description="JGLOBAL_CHOOSE_CATEGORY_DESC" extension="com_mycomponent" label="JGLOBAL_CHOOSE_CATEGORY_LABEL" required="true" />
   	</fieldset>
   </fields>
</metadata>

By reading code quickly, that form field will only show categories which match the current user access levels. I guess we should modify code to exclude access level filter for users with core.admin permission

For the time being, please make sure the account you are to create menu item has the Child Access access level and the he will see the category.

@boddunan PR #40193 should address your issue. Could you please help testing? Thanks !