[Users] Claws & Mutt, Tags?

[Jens Kjaerulff]

I like using both Mutt and Claws (IMAP) for the same email account, and
I'm trying to make my Claws 'tags' work in Mutt too.

I've come across a way of making tags for Mutt using the X-Label header:
http://blitiri.com.ar/p/other/mutt-labels/

So I've made an Action in Claws (Edit message: gvim -f "%F"), which
would allow me to add an X-Label header to all messages already tagged
in Claws (e.g. Tags: example -> X-Label: example).

The problem is, this new X-Label does not show when I view the given
message on the server in Mutt. I suspect this is because I have only
edited a 'local' version of that message on my own computer
(~/.claws-mail/imapcache/).

So my question:
Is there a reasonably simply way to synchronize this local message with
the version on the server (as one could expect using imap), or is there
another way to mass-transfer existing Claws tags to the same messages
on the server, for use in Mutt?