Well, there is always the Sales department! :->
Seriously though, it's very often company dependent.
If you want to be guaranteed continuously in the field, then being a "field service engineer" is your best bet, but that can often be a glorified technician role (not that there's anything wrong with that).
But if you want more design work, then you need to consider an engineering role or company that requires the design to go on-site for various reasons, like design consultation, trials, installation and system testing etc. Power (solar, wind etc) companies are often like this, so getting into power electronics might be worth considering. Many military project also require extensive travel.
And then it also comes down to whether you want local or international travel.
So it's a bit hard to nail down specific job titles or career branches.
Dave.