NOTATIO

Can anyone suggest the best way to draw a tie in this situation?
It's essentially the same issue in both staves of a keyboard part. Is this as good as I'm going to get?

To me eye, if both ties (across both bars) are not the same, they don't look like a continuation of the same thing; but I guess it's inevitable that the second half looks different.

Whenever I see long ties like this in piano music, I wonder if a simple Ped marking would make more sense because of how it gets played in the end (depending on tempo, etc.). Often this is true, but I realize the finger holds/crossing is probably done on purpose here.

Your solution looks just fine, though the bottom one is particularly problematic for a couple of reasons.

1. It looks like the initial Ab tie might be a slur to the F instead of a tie. The extra curvy end points make it somewhat difficult to instantly discern which note it's "pointing to".

2. With the second tie's end points are below the staff line, this could be misunderstood as the a tie between the lowest C's or even a slur between the whole note F and the whole note C.

Tricky trouble indeed! Here are a couple of alternate thoughts that I've seen in published scores (for better or for worse lol), which you may have already tried. They have their pros and cons, just like your solution, but when a lot is going on, I'm not sure one of the cons is completely avoidable.

1. Wider ties. Yes, I know ties are generally kept close, but this can be acceptable as long as it's clear it's not a slur. This solution is complicated by all the whole notes, which you don't want to appear slurred together in that second bar.
2. Split ties (using Laissez-vibrer). Not always ideal, but it does eliminate the "messy-ness" problem.

Not being a fan of Ravel ties, no. 1 looks better to me, but that top tie is problematic. Erasing some background or parts of the tie become more appealing in a situation like this. I think Wes posted recently about this at FinaleForum.

If you are in a daring mood:
Chopin did something like this in a similar situation.

Many thanks, all. It's an organ part, rather than piano, btw.

I think I rather like the S-curve, though sadly, Dorico doesn't offer that for ties, only slurs; the LV ties would also work, though I'd prefer a longer tie that was 'erased' where it got in the way.

I did it in Dorico as a tie.

Oh, I suppose you just moved the anchors...! Dorico has a variety of S-shaped options in the properties for Slurs, and they're not included for Ties.

Yup. I hauled anchors, like back in the day.

The option I like the most is the second one by tisimst, though I would stretch the LV tie to the maximum possible, and then restart it after the B-flat octave.
If I did this in Sibelius, I would create the tie as normal, make it look as the first one, then use white graphics under each note but above the tie layer to mask it. This is similar to what Dorico does with hairpins crossing stems, just manual and can be applied to everything.
The S-shaped options in Dorico are very powerful, albeit quite capricious in their respect, especially across system-breaks, so John's approach is the best in these scenarios!