The problem of empty sealing has been bothering me

The hole problem has been bothering meI don’t know how to deal with it (the hole function in nomad doesn’t work, so does cutting)。Please let me know if there is any way, thank you

Trim line has a bug in Nomad 1.56.
I don’t understand the rest of your question.

Another strange thing, when I try to limit the practical memory, when the rendering special effects are fully turned on, the strange colors appear, which is also puzzling

Is this a hole, or an extracted mesh from mask?

If I trim (use square etc, not line) an object with unchecked “hole filling” I can trim a sphere open. But If I check hole filling like here:

and trim Just a tiny piece, the hole is filled

Go through post effects and switch them on step by step. I guess your “strange colors” are spearing by using curvature. But to be honest, it’s not clear what you mean by strange colors. Do what I said: step by step. Find the guilty one, change settings, or leave it off. Checking manual and tool tips is always a great idea btw.

The rendering issue is a bug from Apple side (like often with graphical issue).
Unless you have a way to replicate the bug, I can’t fix it.

As for the hole, if the mesh has thickness then it’s not a “hole”.
There’s no bug with the hole filling algorithm.

Only if symmetry is used, and the mesh displayed here doesn’t seem symmetrical.