Dug in a little after I saw your question and it appears that the
Predefined Rules are handled as a special case;
Sitecore.Shell.Applications.Rules.RulesEditor.RulesEditorPage and in the
GetGroupedElements method there is an
OrderBy involving a static ID
RulesEditorPage.PredefinedRulesItemId. After trying to follow the decompiled logic, my assumption is that the
Predefined Rules are weighted at the top and then the order by falls back to
Element Folder name. If that is the case, prefixing your
Element Folder name with an underscore or adding your rules to the
Element Folder would likely get them visible toward the top (though neither one of those seems like a perfect solution).
Further note: if you are interested in digging in more, there are 3 processors that get executed out of box during the
RulesEditorPage (in Sitecore 9.0.1 at least):
<processor type="Sitecore.Pipelines.Rules.Taxonomy.GetContextFolder, Sitecore.Kernel"/>
<processor type="Sitecore.Pipelines.Rules.Taxonomy.GetTags, Sitecore.Kernel"/>
<processor type="Sitecore.Pipelines.Rules.Taxonomy.GetElementFolders, Sitecore.Kernel"/>
These pipelines effectively find and aggregate the rules for a given
Tags Definition under the
Rules Context Folder (the multi-list that is sortable and relates your rules to let's say the
Insert Options rule). The result of this
getRenderedRuleElements pipeline is what gets passed into the
RulesEditorPage and eventually ordered and rendered when you click
Edit Rule. I will update my answer if I find anything else while I continue to dig.
Hope this helps.