private void insertEntry(int index, Field key, int bufferId) throws IOException {
		// Make room for key data
		int offset = moveKeys(index, -key.length());

		// Make room for key entry
		int start = BASE + (index * ENTRY_SIZE);
		int end = BASE + (keyCount * ENTRY_SIZE);
		buffer.move(start, start + ENTRY_SIZE, end - start);

		// Store key entry and data
		buffer.putInt(start, offset);
		buffer.putInt(start + KEY_OFFSET_SIZE, bufferId);
		key.write(buffer, offset);

		setKeyCount(keyCount + 1);
	}
Insert the child node entry (key and buffer ID) associated with the specified key index.
All entries at and after index are shifted to make space for new entry.
The node key count is adjusted to reflect the addition of a child.
@param index child key index
@param key child node key
@param bufferId child node buffer ID
Ghidra/Framework/DB/src/main/java/db/VarKeyInteriorNode.java