As per the D365FO version 10.0.14 the Default description parameters functionality has been changed so that the Project - posting, ledger cannot be defined to include transaction description on the voucher line. Up until the version .13 by leaving the Text field empty, a user could define the voucher line to include the description from the project transaction. This was changed in the version .14.

I suggest the Default descriptions functionality to include possibility to inherit transaction level information to the voucher line.

It appears there are transaction types, that cannot have user defined parameters (%4-%6). One of the major ones being the type Subscription. It would be excellent to be able to define for example project invoice number on the subscription accrual voucher line.