Whenever I try to create a group from ingame or console with config set to "yaml-combined" I get a success message saying the group was created, but when running listgroups the list is empty (not even "default").
Looking in the yaml_storage subfolder a file called actions.json is generated listing the actions I have taken, but the groups.yml only contains "null".
If I add permissions to a user the combined users.yml is created, the same goes if I create a tracks.yml.
If I switch to yaml (not combined) it creates the sub folders and individual files for users, tracks and groups.
Tried with 4.4.1 and 4.4.31 under both latest Spigot and Paper.

Quite possibly, I'm just used to how I did things a few years back (PermissionsEX I think), cutting and pasting large chunks of permissions between groups when I was reorganizing and dividing up who could do what.
I will get there, just a bit of a learning curve, but now I have something working at least.

Yaml-combined is a bit buggy.

We also recommend to not use yaml storage. Better stick with the default h2 for best performance and storage usage.

Thank you. It's been a frustrating evening trying to figure this out with the help of the helpful Discord people. I honestly would prefer an human readable option, but I've now installed and got MariaDB working.

The web editor is a much better solution than editing files manually.

Thanks for reporting, this will be fixed in the next release.