So you’re using something like this in your pre/post scripts and just taking the hit on password being in script files?
net use \\myServer\myShare /user:myUser password
net use \\myServer\myShare /delete
Have you tried saving it in the Windows key manager to avoid needing the scripts? (Granted that lets the account access the share even when not backing up so I understand if that’s not your goal.)
Control Panel → Users → Windows Credential Manager & enter credentials with the device name (myServer)