Piece by piece,vine by vine. One at a time til it's cut back hard. the new growth which will soon follow will be more manageable and you will have enough cuttings afterward to start a whole new plant(which could be re-incorporated later if desired). :)

I'm not sure you're sure what you want this plant to look like. Looking at it should be pleasing, we can all agree on that, that's the whole point. At the beginning, you say you want to keep the size of it with more leaves, but later you seem unsure what "more pretty" would even be.

What Asleep suggested is perfectly reasonable, something most long-term plant owners have done. But wow, you've got some split leaves forming there, your plant has become a teenager, so to speak, because it's firmly secured to something above ground, for a while. Definitely not something all potted vines will ever get a chance to do.

I might encourage you to clean it up a bit by removing the dead leaves, any dead stems, then repotting as-is, firmly attached to the trellis, removing only as much old soil as possible without knocking the different parts of the plant apart. I would hope that would give it a boost without disrupting the maturity, but someone who's done that before would be needed to confirm or deny.

Then, if you weave the dangly bits back into the main plant, or even just lean them in there, it would look more full. In time, they will secure themselves in place if possible.

Making some cuts would inspire the stumps to sprout new tips. I'd find a section that doesn't have mature leaves attached to it, probably one of the stems that's dangling, not secured to trellis, cut it so that 3-4 nodes remain above the soil. Hopefully it will grow one or more new tips. That would also be a good way to get more fullness at the bottom and middle.

Maybe you could find some type of taller supports you could add to what's already in there to continue the upward trend of your grand old vine.

If these ideas intrigue you, you may enjoy this more in-depth discussion which has a lot of pics if you scroll down.

Actually I didn't notice the split leaves til Purp mentioned em...which leads me to another option...a moss pole would allow it to continue upward and grow larger and larger leaves.

Thanks for pointing that out Purp,..I do believe my vision is going! lol

Yeah, I didn't see them right away either. Could this be regular ol' heart-leaf Philo doing this?

Never let em go quite long enough to ever find out. Not too sure if they even split their leaves but all the aerial roots make me think it is well on it's way to doing something along the lines of adult growth. And a moss pole would certainly encourage that. :)

IKR! Doing what I can with the vines in the linked discussion... Lots of big leaves, but definitely no splits yet. It is possible for P. hederaceum, if that's what the plant we're discussing is. Could be a baby Monstera. I wouldn't know how to tell the difference from this pic.

Deliciosa? HEYYYYY....didn't think of THAT!

VERY possible!

On that note I would DEFINITELY run it up a pole! :)

Well, I didn't know what the split leaves were about. In the past I would just make the plant small again but as I said, this time I just neglected it for a very long time. I was actually thinking that the splits were a negative indication and further proof that this plant needed attention.

So if I just let it keep going now, what kind of support do I look for? Is a "moss pole" the best? I assume that's a tall rectangular thing with texture? There are lots of other types of supports and as long as I'm getting a new thing I might as well get what the plant wants.

If that is a moss pole, is there another name for it? Googling moss pole doesn't return anything.

Thank you for this advice.

No problem! :)

I searched a bit myself and found this...

Here is a link that might be useful: an older discussion