Bridge 3.3v to GPIO output pin as a manual trigger?

My board is a Feather Huzzah ESP8266. I have two GPIO pins set pinMode OUTPUT and wired to the 'set' and 'unset' pins of a relay board (featherwing latching relay). When bringing either pin high for 30ms, the relay is triggered appropriately.

Can I use a momentary switch, connected between the ESP8266's 3.3v pin and the GPIO pin to give me a physical trigger of the relay?

Below is the schematic showing the set and unset pins.

I don't know if I can apply power to the GPIO pins in OUPUT mode, or if adding the switch will cause any issues with the set and unset pins sensing low again after the button push.

(My other potential method of solving this would be to use two more GPIO pins pinMode INPUT_PULLUP, and trigger the output pins when I sensed low on the input pins.)

You don't want to apply a power rail to a pin which is set to OUTPUT at the opposite rail. That's a short, and large amounts of current may flow. Use the input pin with pullup resistor method instead.

Basically if the OUTPUT pin is set to LOW, and I connect 3.3v to said pin, I'm sending the voltage directly to ground, resulting in as you said, a short.

If I were to place a diode between the GPIO pin and the relay trigger, and then wire the momentary switch between 3.3v and the relay trigger, would that work?

(This is mostly academic at this point, as I think it would be easier to just use another two GPIO pins.)

Yes, a diode would work. That would make that I/O pin either high or off, but not low. But the diode would block current flow into the I/O pin.

I don't know how you read your schematics. Very light grey on white. Unreadable, at least to me.

Very light grey on white

On my monitor, the schematic is red on white and easily readable. The text, not so great.

I've made some adjustments to the design and successfully prototyped by connecting the momentary pushbuttons each between ground and GPIO pins set pinMode INPUT_PULLUP. I'm not sure why I was trying to 'save' pins when this was the simplest solution!