I have just come inside after having to replant a once beautiful coleus which had been massacred overnight just like the OP's photo, only mine was a smaller plant, newly bought but plenty of leaves and healthy.
I've put it into the pot it was bought in for now, with fresh compost and put the pot elsewhere in the courtyard. It was sited next to a blooming RUDBECKIA, the one with yellow petals and dark red throat. It also was damaged with the petals of two flowers eaten away.
What can I do to stop a repeat?
I had to remove all clumps of yellow primroses earlier this year due to leaves and petals being eaten. No slugs seen in daylight nor slimy trails.
I am in South Surrey UK
Advice appreciated.

Hard to say without catching the culprit but I have watched squirrels tear Coleus leaves off of plants and take them up into a tree out of sight.

I didn't read through the old discussion but it probably says what I am thinking, that the original pic starting this discussion looks like caterpillar damage. They can do an amazing job at blending in. Check all around to see if you can find one (or more.)

@RubyVann
Read the responses to the original poster. They apply to you too except since you live in the UK, you may have other pests not mentioned. But the advice would be the same. Look for caterpillar frass on the leaves first. Some caterpillars turn into the color they are eating so look carefully. And then take a flashlight at night and look around a few times and see what you find. Take a photo if you see anything. ID it and see if it could be the culprit.

ID apps are good too .. if you can get a pic

Anbagdi said:Hi all, I have bought a coleus plant 1 week ago and recently the holes have started increasing... more and more holes are coming on the leaves.... 

I do not have any pets in my house.
I have kept the plant outside in balcony and temp outside is close to 70 F.
Is it because of insect? I have tried to look each and every leave but cannot find anything. So what you recommend?

Any spray I can use to help them?

Depending on where you live, it may be under attack by mites, Japanese beetles, or aphids. I would keep some ladybirds and spiders in there with your plant under a net.

Hey all,
I've had some issues now with caterpillar or green inch worms, maybe both but they are p****ing me off, they're pooping - so easily to find but they keep coming back. I sprayed some Yates pyrethrum spray but it killed my coleus, now I'm testing out hydrogen peroxide on another infested one but I'm not very hopeful. Is there a spray I can use that won't kill my coleus but incinerate these little things? Thanks everyone

Hi & welcome! Those are beautiful Coleus! If you see a caterpillar, you can manually remove it from your plant. I throw them into the mowed area to be bird food.

I put them on the bird bath. I also just manually remove caterpillars.