Not only in fundamental wave physics but also in technical areas such as radar and communication systems, high-frequency magnonics is increasingly attracting attention. Here, time-resolved scanning transmission X-ray microscopy is used to directly image high-frequency spin wave propagation in cobalt-iron waveguides at excitation frequencies above 10 GHz. In addition, an excitation technique is presented, which allows for versatile pump-probe experiments with radio frequency currents up to 30 GHz. With this approach, a global sinusoidal magnetic field excitation is applied to induce spin waves from the waveguide edges. Amplitude, relative phase, and k-space information as a function of excitation frequencies and static external fields are observed, matching the theoretical predictions for confined waveguide structures. In doing so, the foundation for high-frequency multimode spin wave excitation and propagation at the nanoscale is laid, which can be a prospective path in radar and communication systems.