[luatex] applying ligaturing functions

[Thomas]

For what I have in mind, it would be best if after hyphenation and before ligaturing is applied, I could manipulate the node list while applying automatic ligaturing for each ligature separately.
Is this possible?
I thought I might be able to use the ligaturing callback for this. However, the problems start with the fact that it is not clear to me how to disable ligaturing in the first place. There are several methods described, but all of them seem not to be applicable in the most obvious way.
The \noligs command expects an integer. - What kind of integer? I tried it with a Unicode number, but that didn't work.
I assigned an empty function to the callback, with no effect.
I also tried the method of setting the callback to false. Again without effect.
Also, it is unclear to me how to apply the ligaturing function (same with the kerning function) of the node library. At least a simple "head = node.ligaturing(head)" does not work.
Unfortunately these things are explained only very briefly in the reference manual.
Are there any sources where one can get further information? I can't find anything on the internet.

Can someone help me here? Thanks in advance.
Thomas
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