Solution: Please comment on the file to make the dropdown menu got back to its normal state
These are the files that were changed to fix the issue:
1. app/code/Bss/GuestToCustomer/view/adminhtml/web/css/source/_module.less
2. pub/static/adminhtml/Magento/backend/en_US/css/styles.css (in order not to redeploy static content)
Please check the video for the details.
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