For example, if one wanted to trigger the benefit of the Mobile feat, wherein you can move away from a creature you made an attack against without provoking an opportunity attack, can you choose to miss the attack on purpose?
The mechanical benefit of this over taking the Disengage action would be that you can use the rest of your attacks from the Extra Attack feature, or still use TWF's bonus action, or potentially save an "on next hit" ability or effect for a different non-adjacent creature on the same turn without taking an attack of opportunity from, or damaging, the currently adjacent creature.
Best Answer
No, you can't.
I will essentially replicate my answer from here: Can I choose to fail the ability check for Dispel Magic?
5e works based on three steps.
Here, we are working in Step 2. If you choose the Attack action, what you want to do is attack - and hit - a creature or object. That's what your character wants to do - actually attack. If you choose that action, you can't choose to miss.
On the other hand, if you choose the action "pretend to attack", you did not attack, thus features that depend on actually attacking will not trigger - that is a completely different action.
Essentially, your character has no concept of an action which would be "make an actual attack, but force a miss" - either it makes an actual attack or it pretends to attack and misses, but again, these are different actions and only one is the Attack action defined by the rules.
As Gandalfmeansme mentioned, though, you can force yourself to bad luck using improvised weapons, which you are not proficient with (and as a Monk, you will be using Str instead of Dex, which might as well be a dump stat), and throw yourself in the ground for disadvantage (or, depending on how your DM rules it, just closing your eyes before attacking and being subject to Blinded condition).