Typo on my part. It drops you from Path to Speed. If they give you an "except maintain speed, change that speed in the FMS and it will do VNAV Path just fine. Don't touch the panel. Do all speed changes in the FMS. Set the current (I forget the page) and then set future on the Legs page. It does PATH really well then as long as you follow "add drag" cues. You can set the current speed in the FMS almost as fast as you can on the panel.
It's been about a year since I've been in a SWA cockpit but I was pretty regularly until then. I always cringed watching the crew doing VNAV, especially the Captains. FO seemed to know it better but the Captains always wanted to ignore "add drag" and roll in a vertical speed or a higher airspeed instead. That or kick off the autothrottles and pull it to idle for all descents. They also had a tendency to set all the speeds manually on the panel and then wonder why it wouldn't do Path. One dropped the gear 25 miles out of San Diego instead of using speed brakes. "I know the company says we can use speed rakes with flaps now but I think it weakens the flaps and I won't do it." to the FO when he questioned him. Same guy refused to use the autothrottle for the descent. He was the cliché of the old Captain who refuses to modernize or change his ways. Old school -200 pilots who doesn't understand all the information on his non-dial screens or how to use the automation.
I'm probably painting with too wide a brush but it was the same things I saw at Hawaiian when we started doing VNAV on the 767 and until I was taught by that one check airman, I was doing the same.
Sorry I'm late to the VNAV nerdery. It's been a minute since my P8 days, but I believe you're looking for the VNAV Cruise page, I think it was page 2 (or whichever VNAV page is active depending on your phase of flight). The thing I've seen bite people on this is: if you get a speed restriction at altitude, they put it in the cruise page, but not the descent page. So for example, VNAV thinks it's flying 250 KCAS at altitude, but 300 for the descent, and it draws the Top of Descent point and the descent path based on that. I've seen people distrust VNAV for things like this, but in reality it's doing exactly what they told it to do, they just didn't fully understand what they were telling it to do.
Never heard of the EAI trick, but the box also allows you to plug in descent winds (my turn to forget, I think it was based on waypoints for climb and cruise, and altitudes for descents), so if you want a shallower descent, you can just tell it you have stronger tailwinds than you actually have.
