Pretty much like halibabica wrote, but let me explain it a little.
Let's make a simple level with one start point and two exit points. Name this level "multiexit". Now, move mouse cursor over the first exit point and press "E" button, then type name of the level you would like to be connected with this exit point. For now, let's type "multiexit1" there. Then move cursor over second exit point, press "E" and type "multiexit2". But right now we don't have any of these levels, so both exits would lead us to the finish. Make simple "multiexit1" and "multiexit2" levels with one start point in each one, start "multiexit" level and try to travel between levels by yourself.
But there is more!
You could also edit start points. Let's try it. First, let's edit our "multiexit" level and add an unreachable part with second start point and some loot over there. Then move mouse cursor over start point at unreachable section and press "E", the same way you did with exit points, and type "multiexit2" there. Now if player would get to "multiexit" level from "multiexit2" level, he will start there instead of the original start point. So, we need to add an exit from "multiexit2" level. Actually, let's make it a little bit more interesting and add several exits, which all but one would lead player to "multiexit1". Notice, what you don't have to edit every single exit point manually. Press "Edit info" icon and keep press "Enter" until you have to name next level. Type "multiexit1". Now, any unsigned exit on current level will lead to "multiexit1". Finally, edit one of exits to lead to "multiexit" level.
Here is an examples you could try.
