Yes. This is just from earlier this year, but still; https://www.cbc.ca/news/politics/poilievre-europe-travel-9.7108961
Sheer did it too: https://www.cbc.ca/news/politics/scheer-united-kingdom-trip-1.4563485
https://macleans.ca/politics/ottawa/mr-scheer-goes-to-india-for-some-reason/
Rona Ambrose: https://www.ipolitics.ca/2017/04/11/trudeaus-enjoying-a-weird-truce-on-trade-with-the-conservatives/
Part of it is certainly about projecting an image to the people at home, but I think it's helpful to remember that the Opposition leader is (typically) an MP as well, and meeting with international leaders is an opportunity to learn and share with your counterparts.
None of the leaders they meet with are confused about their roles, lol. Sure, he or Danielle Smith could be making shady pacts and schemes but that's a different thing than someone trying to pretend they can set policy.
Another benefit of people traveling is that maybe the international leaders just vibe better with them than the members of the current government. Maybe real will recognize real and someone will be straight with PP and get to the point about what the US is actually after and he can bring that insight back home. This is an extremely generous framing but I'm choosing to be kind here lol.
ETA: I went through a list of leaders of the official opposition (https://en.wikipedia.org/wiki/Leader_of_the_Official_Opposition_(Canada)) and searched leaders who were not just placeholders (Candice Bergen, Erin O'Toole) and stopped at Mulcair because that was almost 15 years ago. I did miss Rona Ambrose in my initial post because I forgot she existed I guess, but she did it too. I have added her.