Assuming your text is something like this, with blank lines in-between each block?
Those blank lines are in effect a return followed by a return. So, that is something that can be used.
⇧⌘↓ will select all from the current cursor to the end of all the text.
That can be copied and put into a Variable (in my example, called LOCAL__Variable)
The double returns in LOCAL__Variable can be replaced with something else that Keyboard Maestro can use to split up the variable into numbered chunks - I changed them to @@
The first part of that variable  can then be isolated using the syntax: LOCAL__Variable@@
And that single chunk can be copied to the Clipboard.
EXAMPLE Select All Text up until Next Blank Line.kmmacros (28.5 KB)
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