TriSage said:

Does Sage 50 have the ability to post a single journal entry that has multiple dates and vendors?

No.  Accounting information can only be entered against one vendor at a time, within the Accounts Payable module structure of vendor orders, purchases, and payments.   You can post a single payment to any number of invoices, but only to one vendor.   And you can put in line comments for each line of a journal entry, but they are only notes.  

TriSage said:

It would be a huge time saver if the journal entry would have drop down lines with dates, vendors and debit and credit accounts

What you describe sounds more like a 'Batch', than an 'Entry'.  Because Sage 50 is an 'online transaction processing' system, each individual entry is processed immediately, and there are no multi-entry batches like you would find in the old DOS ACCPAC.

If you need to attach additional information about specific entities (actual projects, vendors, customers, customer hair type, breed of pet) to accounting journal entries, look at using Projects.