How can you set the network fee with sendmany or the equivalent Blockchain api, or the Electrum CSV import?
For example i want to make 30 payments in bulk and i want to pay 0.00001 network fee for each payment, is it possible ?
It is not necessary to do so, and the fee won't be identifiable as independent to any one transaction, it would just appear as one fee of 0.0003 in that case.
The required fee is based on the data size of the transaction, not directly the amount you are sending. The standard minimum fee is 0.0001
per kB. As the size of the transaction will result from both the number of recipients
and from the number of UTXO inputs that are used in the transaction (which you do not have as much control of), you risk either paying too much (not a problem) or paying too little (more of a problem).