Choosing Your Server Software
The Software tab for 7 Days to Die only offers the Public branch — there's no beta or experimental track to switch to. If you do change software settings, saving still requires a server restart, which Spawnly confirms before applying.
For save data and configuration files, use the File Manager (Files tab) — there's no dedicated World or Properties tab outside of Minecraft. See Installing Mods on Your 7 Days to Die Server for what's currently possible around mods.
Next Steps
Read Installing Mods on Your 7 Days to Die Server before experimenting with any mod files. Take a backup first — see Managing Backups & Restoring Your Server. Since 7 Days to Die is monthly-only like most games on Spawnly, Hourly vs Monthly Billing: Which Games Qualify explains how that reservation works.