Rider UnityEngine settings for Prefix & Suffix not saved
When saving the preferences for the UnityEngine plugin for Rider 2021 the settings for Prefix and Suffix are not going to be saved in any of the setting layers.

I can't recreate this. If I save to the personal layer, I get the values written to .sln.DotSettings.user, and if I select team shared, then it's written to .sln.DotSettings, and the values are visible in the options page when I reopen the project. Could you check in .sln.DotSettings and .sln.DotSettings.user for a line like this, please (the GUID should be the same):
<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=5f0fdb63_002Dc892_002D4d2c_002D9324_002D15c80b22a7ef/@EntryIndexedValue"><Policy><Descriptor Staticness="Instance" AccessRightKinds="Any" Description="Unity serialized field"><ElementKinds><Kind Name="UNITY_SERIALISED_FIELD" /></ElementKinds></Descriptor><Policy Inspect="True" Prefix="foo" Suffix="far" Style="aaBb" /></Policy></s:String>
Yes, it's a syntax only a computer could love - an XML blob inside an XML value, but you should be able to see the Prefix and Suffix values.
I'm closing this due to inactivity. Please feel free to comment and we can reopen.