Kosmo,
Are you referring to the list of tags in the Sidebar More Tags list?
If so this is defined in $:/core/ui/MoreSideBar/Tags and its filter is found in $:/core/Filters/AllTags!!filter and reads [tags[]!is[system]sort[title]]
So yes it is sorted by title.
The following button will "tag all the tags" with tag sort, provide a list to drag and drop into the required order and the correct filter to use once setup.
<$button>
<$list filter="[tags[]!is[system]sort[title]]">
<$fieldmangler>
<$action-sendmessage $message="tm-add-tag" $param="tagsort"/>
</$fieldmangler>
</$list>
Tag Tags with tagsort
</$button>
;Reorder below or in the tag pill <<tag tagsort>>
:use the filter `[all[]tag[tagsort]]` in a new or modified sidebar tab
<<list-tagged-draggable tag:"tagsort">>
Regards
Tones