Over the past two decades, developments at 3rd generation synchrotron light sources enabled x-ray studies of magnetism at high-pressure utilizing diamond anvil cells, under simultaneous application of high magnetic fields and low temperatures. Techniques such as x-ray resonant magnetic scattering and x-ray magnetic circular dichroism (XMCD) leveraged high flux density and energy/polarization tunability to provide unique insights into competing interactions in correlated electron systems. APS-U, a 4th generation synchrotron light source to come online in 2024, will provide increases of two orders of magnitude in coherence fraction and flux density of sub-micron x-ray beams. This allows extending high-pressure x-ray probes to the limit of static high-pressure generation, as well as enables in-situ imaging of electronic and phase inhomogeneity at near nanoscale dimensions using techniques such as resonant dichroic ptychography and real-space XMCD tomography. This talk provides an overview of previous developments at APS and upcoming opportunities at APS-U beamline POLAR.