This should be a valuable feature but it is beyond my skills to implement so just mentioning it FWIW;
I strongly suspect the "import mechanism" (the green drop zone thingy) can be used to "split a long tiddler in two". Selecting a text segment and dropping it on the drop zone will create a new tiddler containing this text (actually inappropriately so,
#2157)
I imagine a "split tiddler" feature that takes advantage of this but has a separate dropzone soemwhere and where the new tiddler is by default titled "original tiddler name #2". Perhaps also copying the tags of original tiddler. And instead of having the tiddler "Imported tiddlers" triggered, like in normal import, it is the new tiddler that appears, perhaps in edit mode for immediate continued work.
It is a bit surprising how we don't yet have a solution for splitting tiddlers considering
tiddler philosophy and the problem with long tiddlers and the resistance towards tiddler slices/sections.
As I said... beyond my level tho.
<:-)