It is possible to add separators to Slimjet's bookmarks bar without the use of extensions. To do so visit the following page http://separator.mayastudios.com and drag the "me" link to the bar.
Repeat the process for as often as you want. You will notice that it will add a single separator to the bar whenever you do so. If you prefer horizontal separators instead, drag the "here" link instead to the bar.
I'd add that the site http://www.favicon.cc has a huge number of favicons, including all kinds of separators. Just find what you like and drag it to the bookmark bar. Note that there is a Search box in the mid-left of the page, so you can type "separator" or anything else and search for favicons.
Add separators to Slimjet's bookmarks bar.
Re: Add separators to Slimjet's bookmarks bar.
I like this idea. It makes it more accessible.