Firstly, I'm once again trying to escape from Quicken. But, this time, I working with the Windows version of KMyMoney (Version 5.1.3-e074e7940). I've imported my Quicken QIF export, but they're completely messed up (as expected). Before I spend too much time trying to fix the data, I'm looking to see if KMyMoney will let me do what I need. So, maybe what follows is just because my data is bad and not a function of KMyMoney's report generator.

Initially, I need Investment Transaction Reports of all my investment transactions for a period that's sorted first by investment account and then by date. I can't find anyplace to set the sorting method. AFAICT, those transaction reports always get sorted first by the account, then by security and THEN by date. Plus, the Account field in those reports doesn't actually contain the account. It contain the security. Worse, when I export that report to a csv, it gets exported as how it looks instead of something usable in a spreadsheet. So, once in a spreadsheet, the account names are stuck in the first column all on their own as a header, but none of the actual transactions have a field that contains that account name (again, the Account field contains the security, not the account). So, it can't be sorted.

I was thinking that exporting the data (File > Export) as a CSV might work. But, that exports a single account at time. I'd need to export all transactions from all accounts for the period I'm looking at.

Is there something I'm missing for the sort order? Why are the securities showing up in the Account field of the report instead of the actual Account name (of course, I'd need the security names, too).

I don't think you are missing anything - reports don't have that level of configuration to allow custom sorting.
Within an Investment Account, each security is handled internally by KMM as an Account, thus the confusion on naming.
I suspect you can do what you want, but it takes a bit of extra effort/pre-processing in the csv file. If you copy/paste the account from the section header into each transaction row, you should then be able to sort on the coumns you want. I think all those extra header/footer rows will sort to the beginning or end, so you can remove them at that point and only keep the actual transactions. I actually have some perl scripts I use to pre-process some csv files from reports, not for that purpose, but similar. They save me the effort of manual copy/pasting and adding/removing columns before sorting or other processing.
I don't know if there is a wishlist already filed or not, but I agree that allowing the csv exporter to handle more than one account at a time would be useful. I don't know how hard that would be to implement, but it's just not currently a top priority.