Hi, all. I found some very old posts about this same issue but did not see any posts relating to the 3.x generation.
In a nutshell, I have "Enable default service name" checked but when it comes time to save a new service no filename is filled in. I'm fairly positive this started for me with 3.1.0...which I believe is also the first version that I ever installed via flatpak. It had worked fine for years! I now have 3.1.2 installed and the behavior is the same. It is only a minor inconvenience but I do miss it especially when training a new operator/helper.
System is Linux Mint 21.3. OpenLP 3.1.2 installed via the flatpak provided on get.openlp.org