Split Excel Cell by last Delimiter

Both of the above would work, but here's something a little more digestible:

=TRIM(RIGHT(SUBSTITUTE(A1,"-",REPT(" ",LEN(A1))),LEN(A1)))

You need this formula:

=MID(A1,FIND("~~~~~",SUBSTITUTE(A1,"-","~~~~~",LEN(A1)-LEN(SUBSTITUTE(A1,"-",""))))+1,LEN(A1))

Breakdown:

LEN(A1)-LEN(SUBSTITUTE(A1,"-",""))

Counts the number of times "-" occurs within the cell,

SUBSTITUTE(A1,"-","~~~~~",LEN(A1)-LEN(SUBSTITUTE(A1,"-","")))

Then replaces the last occurrence of "-" with "~~~~~". If "~~~~~" has the possibility of occurring normally in your input, use a different value here.

FIND("~~~~~",SUBSTITUTE(A1,"-","~~~~~",LEN(A1)-LEN(SUBSTITUTE(A1,"-",""))))+1

Finds the position of the "~~~~~" that we just created, and adds one so we start just after it. And then finally, the full formula uses that position and MID() to extract the desired text.