This is a MySQL database so you can enable remote connections yourself through Plesk. You only need to have an admin do it for you if it's a PostgreSQL database.
Added.
It's not possible for users to create subdomains on their own yet either. Added.
For the domains I see you're using Cloudflare so if you haven't already you'll need to create A records for each one with the value 65.19.141.77 and if you want to support IPv6 as well you can create AAAA records for 2001:470:1:1ee::2002.
These types of config are intentionally locked, and we won't be handing over control ever on shared hosting. People do ridiculous things like request us to set the max upload size to 10 GB when their account can only even hold 1000 MB. Settings values like this wrong can cause serious load and downtime for other accounts on the server. If you need to be able to change them yourself you'll have to get a VPS where you have root control over everything and you're the only user on the server. If you want to request a value we can sanity check it and make the changes for you. We can make changes like this on a domain level so only one of your domains uses the new value, and the rest of the server continues using the default.
Let us know if you have any other questions.
You will be able to do this on your own eventually, but for now we can change it for you if you don't like the default.
Let us know if you have any other questions.