I have three Profoto strobes and have no problem triggering them and taking readings with my Sekonic L-758DR. I simply change the mode from Ambient Light - Flash Trigger and it just works.. but what I can't figure out is why I can't change the Modes from Shutter Priority - Aperture Priority in any flash setting on the meter. I should be able to dial up a desired f stop to control depth of field and press the trigger button and have the meter tell me which shutter speed to use but it doesn't! I can only use the default Shutter Priority measurement. Is this a limitation on the 758?

Think of it this way- When you meter is set for electronic flash readings it automatically assumes that the FLASH is the principle and only light source and except for synchronization limitations, the shutter speed, as far as the meter is concerned, is the flash duration- whatever it might be. It "thinks" the camera shutter speed is irrelevant. The only time the actual camera shutter speed impacts the exposure is if you drag the shutter (use a slow enough shutter speed) to admit some or all of the ambient light.

So, if you want to select an aperture for selective focus (minimal depth of field) or to incorporate more depth of field in any particular shot when the flash is you among light source is to either adjust the flash output up or down to accommodate your requirements or adjust the IOS setting.

For this reason, when I recommend flash equipment for studio use, especially portraiture, I usually opt for units that have a very vast and adjustable power range. If you should want to provide selective focus, bokeh, etc., it is just as important to be able to power down your flash system to enable wider apertures as it is to boost the power when more depth of field is needed. The same goes for being able to establish a wide variety of lighting ratios in multiple flash setups or daylight to flash fill ratios when working with flash out of doors.

I use several meters, most of which are older models. Perhaps some of the newer issues can calculate both daylight and flash simultaneously or somehow correlate the separate readings and therefore enable an aperture priority function? I just take separate readings and do my own calculations.

My main point is that when the flash is the principle, dominant, or sole light source the sensor only "sees" the flash at its duration and reads accordingly and only supplies an aperture setting for the power output (quantity of light), at the distance between the flash unit and the subject (or the metering sensor in an incident light reading) as per the ISO setting. Your variation controls are distance, power output settings, attenuating the light with diffusion material, using neutral density filters on the camera, or the lights or employing bounce techniques or utilizing light modifiers. The camera shutter speed kicks into the equation when you eliminate or admit ambient light.

In certain thyristor and TTL controlled flash systems, the flash duration can be anything for 1/300sec to 1/10,000 sec or less but the meter doesn't care, it is just interesting in light quality.

The exception to the rules is in some High-Speed (HSS) Flash systems that are designed to synchronize flash with focal-plane shutter beyond their usual maximum synch speed, the actual camera shutter speed will influence exposure. In this case, the flash tube glows much like a continuous light source.

As usual, you have a great response from EL.
I use the same meter. OUTSIDE it will show you the percentage of flash to ambient. Generally, around 40% flash is the most pleasant and natural-looking. The cool thing is adjusting the shutter duration to darken or lighten the background in relation to the flash. There is a limit, of course, as I cannot go shorter than 1/250 without exceeded the sync speed. For some studio strobes, even 1/250 is a touch fast and I go to 1/200.

In the studio, shutter speed is virtually of no consequence as long as it is short enough to kill any ambient.

Nice work.