In investments, Stock Split is not a choice for available new transactions.
What version of Quicken Mac are you using? It's currently in the Transaction Type dropdown menu:
@Gary Warnalis It appears you may not have the "Type" column visible in your register. This is where you would see the pull-down menu offering all the types of investment transactions. Compare your screenshot to mine here (and @Jon's above), noting that the field after Date is "Type":
Clicking in the Type field displays the menu of investment transactions types:
If the Type field is not visible in your register, then every transaction will be the first Type in the invisible menu, which is Buy.
If I'm correct that Type is not visible in your register columns, click the Columns icon in the bottom toolbar and click on Type to make it appear.
I am on version 9.0.3 and when creating a new transaction I do not get the up / down pull down menu on the screen. The only choice when inside Investment Transactions is "Investment:Buy".
Screenshot in version 6.0.6
I don't know how you're getting that, so far I haven't been able to duplicate that with any account type or subscription level. And I don't know what you mean by "6.0.6", I don't believe there ever was a Quicken with that version number (it appears they went from 6.0.3 to 6.1.0).
You are correct. The Type Column was NOT selected on the account in question, and once I chose it, I can see stock split in the New Transactions for the account. Thank you, Jacobs.