You can't add new subaccounts to a budget in GnuCash, or change the names of existing subaccounts.
The GnuCash Tutorial and Concepts Guide says, in part:
Even before you begin to make a budget, it’s important to have given
some thought to your account hierarchy. For example, if you want to
budget a certain amount for your electric bill and a certain amount
If you want it to be tracked as an investment - you should set it up like you'd do with any other investment. You'll record a new asset "10USD" with value of 600RUB (your equity).
When you sell - you'll transfer that asset to your checking account as "800RUB", which will force you to add 200RUB from somewhere - you'll add a "foreign ...
The short answer is NO, GnuCash can't do that at present.
There's useful information on Scheduled Transactions in https://wiki.gnucash.org/wiki/Scheduled_Transactions - including examples of performing simple calculations directly in the register, and using variable names in formulae to have GnuCash prompt you for an input value. There's also examples of ...