Want to purchase TGV tickets from Bern(e) to Dijon using SBB website, choosing "pickup at rail station" option. But my travel day is on a Sunday and it appears that the international/TGV ticket office at Bern rail station is not open.

My question: can I pickup these tickets at the regular/Swiss/national ticket office in the Bern station?

There isn´t an "international/TGV ticket office" in Bern. You can pick it up anywhere on a rail station, or better, in the SBB travel office in the station.
Or, if you like some peace of mind, just pass by the station on a saturday?

Thanks very much. Unfortunately, I'll be "up in the mountains" on Saturday, so I can't get to the station then. Could get to someplace like Interlaken station though.

It doesn´t really matter - the distinction between "international" and "domestic" windows is purely for "crowd control". They all have the smae computers accessing the same booking system. I have regularly bought my tickets to Germany and France from domestic counter in Zürich. Sometimes, if the lines are long, you get a reproachful "please, next time go to the int. counter"

Danke, merci, grazie, grezi....