This has been suggested dozens of times. If you search the forum for “previous balance on sales invoice” you can read some of the discussions about it. In fact, you participated in a topic just one week ago in which the developer already expressed his plans: Adding previous balance and/or closing balance to an invoice? - #4 by lubos.
Please do not start new topics when there is already more than one thread on the subject.
Likewise, search the forum for “barcode”. You will find many discussions on this poorly defined term. What “features” do you want? To generate barcodes? Read them? Print them?
Lastly, please do not combine requests or questions in topics. That violates forum rules and lessens the chance of obtaining action.
I am closing this topic.