Your plumber after taking the entire system into consideration should be able to move it but it is touch to tell what can be done from the limited info given.

Where can new tub drain be relocated to? Are there other walls in the room?

I bought a center drain tub and need to move the drain to the center of the room. The wall opposite of picture is external which must will be load bearing as well but I haven’t opened that to see.

Been there, done that! We had the same issue when we remodeled our master bathroom 9 years ago. We also changed from a tiled alcove tub to a freestanding tub that we rotated 90 degrees, so the vent pipes had to be moved. My GC and the plumber figured it out pretty easily.

What was the solution ?

If you use 2" piping and your slope is code minimum 1/4"/ft. you have 8 ft. before you need to vent. Hopefully you can vent at another wall and reconnect to existing vent or run new.

That’s a good point we have a sink and vent on the other wall. Since we are moving the drain to the center therefore we can move the vent to the other side as well and not have to notch the header.