Round Trip button erase my Route

Hi !

I just discovered the round trip button and I find it really useful.

But it erase my route when I click it.

Simple example: let's say I want to go from Toulouse to Albi, via Castres.

So I plan my route, first go straight East to Castres, then North to Albi.

When I click "round-trip", it erase everything and propose me to go directly North-east to Albi (and thus remove the Castres first stop), and it add a inward trip nearly parallel to the outward.

I was expected a button to get me back to the start of my trip at the end, not to propose a totally new trip.