Problem

In ServiceNow, the Knowledge Category Picker (used for the kb_category field in Knowledge articles) opens a dialog window using the UI Macro kb_category_reference_lookup.

However, the dialog’s height is fixed to 150px, even when using:

dialog.setSize(width, height);

This causes the category selection dialog to appear too small, cutting off most of the content.

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Root Cause

Inside the original macro, the dialog window uses a container element called .colview-container, which enforces a fixed height of 150px.

This style is applied dynamically after the dialog renders, so modifying the dialog size directly does not take effect.

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Solution: Create a Custom Macro Override

To fix this, create a cloned UI Macro and override the height of .colview-container dynamically during the bodyrendered event.

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Steps to Implement

Step 1: Create a Custom UI Macro

1. Navigate to System UI → UI Macros.
2. Search for the macro kb_category_reference_lookup.
3. Open it and click Insert and Stay to create a copy.
4. Name the copy:
   kb_category_reference_lookup_custom
5. In the XML content, locate the part where the dialog rendering logic is present:
   js dialog.on("bodyrendered", function() { var wndw = $j(window); var dlgSecPart = $j('.drag_section_part'); dlgSecPart.css('width', 'auto').css('height', 'auto'); ... });
6. After this (var wndw = $j(window);) logic, add the following code snippet:
   js var colContainer = $j('#body_kb_categories_dialog .colview-container'); // Override the default height colContainer.css({ 'height': '500px', // or use '70vh' for responsive height 'max-height': '75vh', 'overflow-y': 'auto' // enables internal scrolling });

This ensures that once the dialog body is rendered, the .colview-container expands to the desired height and supports scrolling if the content exceeds the visible area.

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Step 2: Update the Dictionary Attribute

To make the form use the custom macro instead of the default one:

1. Go to System Definition → Dictionary.
2. Search for the field kb_category on the kb_knowledge table.
   kb_category
3. Open it and locate the Attributes field.
4. Update or add this attribute:
   field_decorations=kb_category_reference_lookup_custom
5. Save the record.

This links your custom macro to the Knowledge Category field.

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Result

After applying the fix:

• The category picker dialog opens with increased height (500px or 70vh).
• The content is fully visible with internal scrolling.
• The change is upgrade-safe since it uses a custom macro.

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Notes

• Adjust height (500px or 70vh) as needed.
• Using viewport units (vh) keeps the dialog responsive across screen sizes.
• Avoid editing the out-of-box macro directly to maintain upgrade safety.

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Summary

If your Knowledge Category Picker dialog appears too small, the issue lies in the fixed height of .colview-container.

By cloning the macro and overriding the container height in the bodyrendered event, you can fix it easily.