Four types of LOWEST, LOW, STANDARD, and HIGH are available for setting the drive current value of GPIO.
It is not possible to apply a desired current setting to a desired pin, so there is a choice between the current value (alt. drive strength) specified for each port and STANDARD. For example, if you set LOW to Port-A, the GPIO belonging to Port-A will use either LOW or STANDARD.
alt. drive strength is set by GPIO_Px_CTRL, but you can easily set it using emlib's GPIO_DriveModeSet.

When setting the mode to Push-pull in the pin settings, there are two choices: MODEn=0b0100: Push-pull and MODEn=0b0101: Push-pull with alt. drive strength. Selecting 0b0100: Push-pull results in the STANDARD setting, and selecting 0b0101: Push-pull with alt. drive strength results in the alt. drive strength setting specified by GPIO_Px_CTRL. The mode can be easily set using emlib's GPIO_PinModeSet.

If you want to use two or more settings other than STANDARD, you need to plan the pin assignment. For example, if you want to use LOWEST and LOW, set port A's alt. drive strength to LOWEST and port B's alt. drive strength to LOW.

Please note that the total current for the entire device is specified, so please use within that range. (Is the maximum rated current value specified?)