You're welcome :) It's OK I wasn't expecting thanks. It's a discussion not an advice clinic 
I agree that two warnings is too many, or actually, more that these warnings are too late because the behaviour has already happened - if you're wanting to avoid or minimise use of punishment, then the correction needs to come earlier, when it can be more of a nudge in the right direction. At the age when they are drawing on furniture, they don't actually have the impulse control to comprehend being given a choice to behave well vs behave poorly, so if you give them the chance to make the choice, you're actually setting them up to fail, and every time they fail (do the behaviour you don't want), it reinforces that behaviour, even if you "correct" it with a punishment. So what I would do is when I first see the child getting the pens or first gave the child the pens, I would remind them "Remember, just on the paper, OK?" and defo keep an eye. If I noticed that they were wandering a bit, e.g. missing the edges then it would be a reminder "Be careful of the table" - and possibly getting a piece of newspaper or something to put underneath as a buffer zone, if I hadn't already done that because I remembered from last time. I would aim, ideally, to stop/intervene before the pen even touched the chair, and either decide that it meant I needed to sit with the child and supervise them much more directly, or if that wasn't possible, decide that the pens need to go away. Not as a punishment or deterrent specifically, although of course the child might be upset! But more because I'm not able to supervise closely enough at the moment so the activity isn't appropriate. As it's not a punishment, I might distract the child with another activity to cheer them up, or suggest an alternative to the child such as drawing with pencils instead or getting out the aquadraw. I'd probably also decide that pens still need to be a supervised only activity, and I'd place them up out of the child's reach and they'd have to ask for them and wait until I or somebody else was available to supervise, or wait until pen drawing was offered. Again, not as a punishment - just in order to reinforce correct pen usage, and avoid reinforcing a scenario where she draws on furniture, even if she is punished for doing that. You can control their environment to this extent, this is not a difficult thing to do, even if you have older children you can tell them to keep the pens out of reach of the little one unless they are supervising her. Of course there may be the occasional slip up, but because it's rarer all you really need to do is speak firmly to them to explain it's not acceptable, and make sure to hide the pens better. If you have a very determined child who is seeking out the pens under great effort and insisting on drawing on furniture, that might be a case for punishment as a deterrent - but that's a different scenario, IMO, than most toddler furniture drawing, which tends to happen just because they have no focus and get carried away in what they are doing.
Just my opinion, of course - some people would say that this is overly babying and that toddlers are able to make choices like this. I see it as a shift in responsibility as children get bigger. When they're really little you decide the boundaries (because they don't know!) but you also have control over what they can physically do, because they are small and dependent, which means you can reinforce behaviours you want by steering them into them and encouraging/praising, and avoid reinforcement of behaviours you don't want by physically preventing them. However, as they get older, you can start to let them make small choices which will have consequences (for example, deciding whether to wear a coat or feel cold) but you would definitely continue to prevent most things (like not letting them jump into a pond to find out it's wet and cold). By about the age of 7 they should be making these kinds of consequential choices more than half of the time, so that they learn what it means. The consequences could be natural (forget your coat, get cold), logical (make a mess, clean it up) or generic imposed (hit somebody, lose screen time). You're deciding the boundaries and they're having more freedom to make choices between them, but not too early. Later, by the teens, there's another shift where you move to deciding less of the boundaries and they begin to work out boundaries for themselves, so you stop policing some of their behaviours at all (but might still give advice if needed) - however of course some boundaries are still important for teenagers, and at this point due to their size and amount of time they spend unsupervised out of the house, you're not actually able to stop them from making whatever choices they like - you can only react to their choices in line with the boundaries you've set.