When I use the syntax for tags in the frontmatter that goes without a hash character, like
--- tags: one, two, three ---
then I do not get auto completion for the tags when typing them.
Autocompletion only happens when I enter a hash symbol.
It would make creating frontmatter sections much easier and avoid creating duplicate, similar tags, if Obsidian would regognize that it is in the tag section and offer auto completion for tags here.