Is it possible to search all markers in Premiere?
You can use the Project panel search box to find your specific markers, and even save your search as a Search Bin by clicking the folder icon with the magnifying glass. 



You can then search within each matching clip for the specific marker by first selecting that clip in the Project panel, then using the search in the Markers panel which you can open by going to Windows &gt; Markers




You can find additional information about searching your project in Adobe's help documentation on finding assets.