Do you mean how to add paths so that your .exe files can be run from Qt Creator, or adding paths so that your .exe files can be run without Qt Creator?
In the first case (starting .exe files from Qt Creator) as long as you only have a single version of Qt installed on your PC, there should be no need to add any paths, as I said earlier, Qt Creator adds the path to the Qt dlls for you.
In the second case (starting .exe files without Qt Creator) then there are 2 ways to do it:
copy the Qt dlls to the same directory that your .exe file is in, either manually or by using the windeployqt.exe program
adding the path to the Qt dlls to the PATH env. variable
Note: LIBS += -LMyPath has no effect on runtime lookup of .dlls or .so files
QMAKE_RPATHDIR has no effect on Windows, because Windows does not support adding a list of paths to your .exe/elf file where to find the Qt dlls/so files (works only on Linux and MacOS)
Also on Linux, QMAKE_RPATHDIR is not needed for the first case (starting .exe/elf files from Qt Creator) since Qt Creator does that automatically for you (by issuing a linker command e.g. -Wl,-rpath,/home/user/Qt/5.15.2/gcc_64/lib)