Hi Szymon.
I found by change this post.. i dont know why i didnt respond you. Well, here is the info.
The exit EXIT_SAPLCKMLMVQUANT_001 allow you to change the text .. so you can write 'account' + 'profit center'. I know its possible(the exit is active) but if you want to use it ask SAP, maybe is not a good idea.
This OSS explain how to include aditional fields in CKMLV005, eg the Profit Center. With this, you dont need a profit center substitution in the ml close, only in the original movement (but its better do the substitution in the outbound delivery)
1242114 - Revaluation of consumption Additional acct assgmt features