By default, Open User Map displays the Marker Categories filter and the Advanced Filter Interface (Button or Panel layout) in the bottom-right corner of the map.
If you’d prefer these controls to appear in the bottom-left instead, you can easily reposition them using a small CSS snippet.

Do this

Add the following CSS under Open User Map → Settings → Advanced → Custom CSS:

.open-user-map .box-wrap .map-wrap .oum-map-filter-wrapper {
    left: 10px;
    right: auto;
    align-items: flex-start;
}

🎉 Result

The filter controls will now appear neatly in the bottom-left corner of your map.
This works for both the Marker Categories widget and the Advanced Filter Interface in Button or Panel mode.