JSFiddle - React, Tailwind, and code Playground

HTML

<div contenteditable="true" onkeypress="if (event.keyCode==13) { document.getElementById('ex').appendChild(extractBlockContentsFromCaret()); }">
    <p>One tow</p>
    <p>One tow</p>
</div>
Extracted:

<div style="border: solid green 1px" id="ex"></div>

JavaScript

function getBlockContainer(node) {
        while (node) {
            if (node.nodeType == 1 && /^(P|H[1-6]|DIV)$/i.test(node.nodeName)) {
                return node;
            }
            node = node.parentNode;
        }
    }
    
    function extractBlockContentsFromCaret() {
        var sel = window.getSelection();
        if (sel.rangeCount) {
            var selRange = sel.getRangeAt(0);
            var blockEl = getBlockContainer(selRange.endContainer);
            if (blockEl) {
                var range = selRange.cloneRange();
                range.selectNodeContents(blockEl);
                range.setStart(selRange.endContainer, selRange.endOffset);
                return range.extractContents();
            }
        }
    }