You can use boolean to do this. It's just gonna be slow going. Select one of the objects and give it a boolean modifier. Set the boolean operation to union and set the object to one that is overlapping. Then apply the boolean modifier. This will join the 2 geometries and delete the inner parts. also the original geometry will be left as a separate object. You'll want to delete that. Now use the new object to boolean another overlapping object. Slow but it will work.

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"The true sign of intelligence is not knowledge but imagination".

Albert Einstein