It’s always useful to walk the SJ at an event if you possibly can, to check lines and distances, but coursewalks are not often publicised well. If you check on bdwp or the BE website to see at what time your class (not section, usually!) starts SJing, and what time the last competitor in the previous class goes, you might be able to fit in a coursewalk if it doesn’t clash with your dressage time.
E.g. these are the times for Brooksby Melton. The BE100s start SJing at 12.18 on Saturday, and the last BE80 competitor showjumps at 11.58, so the SJ course should be available for walking at about 12.10 ish.
If I want to watch competitors riding the XC course that I will be doing, then ideally I need to walk the XC from 13.04 onwards.