I recently updated my network from a /24 subnet mask to a /23. I just needed/wanted more address options.

I went to log into a SMB share on my windows computer and noticed that my unraid server wasn't showing up in my windows "Network", but I could type the address in and it was accessible. In my UnRaid Network Settings it shows the route still being 10.10.50.0/24. I've deleted it and added /23 but when I reboot it goes back to /24.

I cant find an option to manually input the subnet mask...How do I update it to the rest of the network with a /23?

Not sure what you think using /23 is going to give you? Cannot see the Use Case where it would be useful.

You should edit eth0 setting instead of delete/add routing table.