Hi @Yue_Wang, Thanks for reaching out about this!
We currently don’t offer a standalone Dev Mode option on the Professional plan. We wanted to keep our plans and pricing as simple as possible, and for most on the Professional plan it’s easiest to combine the features as part of designer and dev mode seats.
However, on the Organization or Enterprise plans, Dev Mode is available as a standalone seat. You can find more details here: Dev Mode for admins
If you require a standalone seat on the Pro plan, you can find a related feature request here from other community members. Please check out the post and vote to show your support:
This post has been shared internally for consideration, but we do not have a specific timeline to provide at the moment. Please stay tuned to our release notes and blog for any updates.
Thanks again for reaching out.