a while ago I've created an asset called "Smart UI Selection" which patches the UI selection process in the scene view. Especially helpful for complex ui canvases.
Check it out here:
* Asset Store: https://assetstore.unity.com/packages/slug/124328
* Forum: https://forum.unity.com/threads/smart-ui-selection-unity-editor-extension.707522/
* Documentation: https://kamgam.com/unity/smart-ui-selection
* Support: https://kamgam.com/unity/support/smart-ui-selection