Currently, there's [x] Only Mine near the beginning of the filter line, and, at the other end, [x] Only Externals. These two are related, even are mutually exclusive, so they shouldn't be check-boxes, and shouldn't be so far apart.

I would suggest something like this:

I.e. radio-buttons in a group; with Me/Mine defaulting on.

I've attached a UI file with the layout.