How do you put another outlet onto conduit
Surface raceways will save you a lot of work in many situations, especially big raceway where you mount receptacles in the cover.  You can add wires from the nearest receptacle on the same circuit to the new receptacle.  These surface raceway products are expensive, some are very expensive, but it's not too hard to work with and you can get a great finished installation without any special tools.  With conduit, you really need to buy a bender and learn how to use it to get a nice finished install.
Of course with conduit, you could just backtrack.  Put the new box under the existing conduit, run a new conduit and wires from the nearest box to the new box.  It doesn't look as nice but it's totally fine.
If you really don't like the idea of boxes at different heights when you backtrack - you could enter the tops of the boxes on the left and exit on the right with pull elbows...

... or, you could run the conduit down at baseboard level and stub 90s up into the box left and right.  That might look a little nicer.  You get the idea, you can get creative.
EIther way, then you'll have clear space between for new boxes.  This will be easier to modify if you add boxes.  You can use a side knockout to backtrack and hit a box set at the same level.