A method for electronically controlled formation of user-defined laser pulse patterns in a synchronously pumped laser based on a semiconductor optical amplifier and an all-fiber resonator is proposed and investigated. It is demonstrated that synchronous pumping allows mode-locked operation with the laser radiation structured as an arbitrary pulse pattern repeatable on each cavity round trip. Direct electronic control of the structure and shape of the generated laser pulse patterns is implemented. The accuracy of the reproduction of modulation pulse patterns and waveforms delivered from a radiofrequency arbitrary waveform generator is examined. The time constraint on the pulse pattern formation in the steady-state mode-locked lasing regime is revealed, as well as the feasibility of the quasi-steady-state regime with on-the-lasing continuous modification of the pulse pattern structure.