Is it possible to set ledgers so when entering new transaction it goes to the date field first?

In 5.1+ there is a (hidden) feature to do that: Make sure to close all KMyMoney windows and open the file ~/.config/kmymoney/kmymoneyrc in a text editor. In the current development version there is a UI feature to adjust the tab order.

Look for the following section:

[General options]

and add the following entries (location within the section does not matter):

stdTransactionFormTabOrder="account,cashflow,payee,category,tag,memo,number,date,amount,state"
stdTransactionRegisterTabOrder="number,date,payee,category,tag,memo,payment,deposit,state"

Change the order of the fieldnames to your liking but make sure to keep all values in the lists. Don't change anything else.

Tried it and it does not work...
Version 5.1.2-3233c181b

Then it might be broken (but it was never an official feature in the 5.1 branch anyway but more a proof of concept).