Pull Request resolves #44764 #45492

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

This Pull Request adjusts the indentation and expand/collapse chevron positioning in the Atum treeselect used for module menu assignments.

The changes ensure that checkboxes at the same nesting level align vertically while keeping the menu hierarchy clear.

This is a backport of #48125 as it fixed numerous reported bugs

Testing Instructions

Create a menu containing parent and nested child menu items.

• Apply this Pull Request.
• Build the CSS assets by running npm ci.
• Log in to the Joomla Administrator.
• Go to Content → Site Modules and open a module.
• Open the Menu Assignment tab.
• Select Only on the pages selected.
• Expand and collapse the nested menu items.
• Verify that checkboxes at the same nesting level are aligned correctly and that the chevrons remain properly positioned.

Actual result BEFORE applying this Pull Request

Checkboxes at the same nesting level are not aligned consistently because the expand/collapse chevrons occupy additional horizontal space. This makes the menu tree appear uneven.

Expected result AFTER applying this Pull Request

Checkboxes at the same nesting level are aligned vertically. Expand/collapse chevrons are positioned correctly, and the nesting hierarchy remains clear.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed