There is not a feature that was made specifically for this, but here are some ways this can be done.
SUGGESTION #1:
Highlight the procedure name in the package code, which would then highlight ever other instance of that name in the code, and scroll through the code to find where else it was highlighted.
SUGGESTION #2:
Use the Find feature (Ctrl+F) in Toad to find all the instances of the name of the procedure, which you want to find the calls for, within that package.