Can we have a link in the header on this site (the mathematics meta site ) to the main (mathematics site), just a simple link will do, it is just to make swiching between them easier.
Speaking as someone whose job frequently involves flipping back and forth from the meta site and the main site, needing to use two clicks to go in either direction is bothersome. We added it to the "help" dropdown in the top right to make a more consistent option than the top left, but it's still two clicks.
Mad Scientist is right, though - in its design, we don't really have room to comfortably link to the main/meta site in the top bar directly. When you've got enough status...
...it starts to get crowded. We want to keep the design in such a fashion that it shouldn't break readily, so even though technically I could see enough space for fitting the word "main" or "meta" up there in the given image, that would possibly cause issues when someone gets even more rep and more badges (as some folks do). I could also bore on details on whether or not "meta" is meaningful as a word to new users, but I think that's getting too bogged on reasoning.
End result is that with this design direction, it is unlikely that is going to change in the native system itself. Manishearth, however, wrote this script to add a Main link to the top bar when viewing any Meta site, as illustrated in this image:
Installation instructions for scripts can be found here. Note that if you have a lot of top stuff from being a moderator with a lot of rep and badges on a site with active flags and suggested edits... the script will cause some clashing and overlap of elements in this scenario. Otherwise, it should be pretty clean to use.