Your Coleus look very healthy! If want to trim them, would suggest maybe trim to about halfway down, about 8-10in/20-25cm, and trim them about 1/3 the way up from a node & 2/3 of the distance down from the next upper leaf node/leaf branchout point. Then ~'pinch' the top stem ends to keep them from losing liquid/sap from the trimmed tops. Would suggest trimming them a varying exact heights, both for aesthetics & to provide for more room for new growth from the individual trimmed tops.
If want to, the trimmed portions can easily be placed in water, where they may root quite readily! Placing them in some water should be done immediately(maybe have a container with some water in it handy when do the trimming). Then, before placing them in some water to root, trim about 3/4 in / 2cm off the bases, slicing at about a 45degree diagonal(the stem should be wet where the slice is made, so like gathered flowers, the Coleus won't wilt) and place them directly in water! After a little while they should root well, resulting in nice new matching Coleus! Good question and good illustration!