Hi RianTan,
Yes, the middled grate can be removed.
Please see the link below for an illustration of removing the middle grate under the "Cast-iron griddle, grates, and wok grate" section and page38 under"Burner grates and components." section of the manual for additional details
How to clean Samsung gas cooktop
https://www.samsung.com/us/support/answer/ANS00049945/
Manual
https://downloadcenter.samsung.com/content/UM/202309/20230920163131327/O_01._IB_FULL_NX60CB831512AA_EN.pdf
To check the availability and compatibility of a middle grate, you can contact Samsung's official parts distributor for customers purchasing Samsung parts or accessories.
Orders can be placed online at www.samsungparts.com or by phone at 800-627-4368; hours of operation are 9:00 a.m. – 6:30 p.m. EST, Monday – Friday.
Should you need more assistance, please feel free to get back to us via the following options:
1. Facebook Messenger: http://m.me/Samsungsupport
2. Twitter: https://twitter.com/messages/compose?recipient_id=18768513
3. Samsung Community: https://us.community.Samsung.com/t5/Samsung-Community/ct-p/us
When you message us, please provide us with this reference number (1147161548) to help our team gather your information.
Have a great day.
^Charles