appimage questions - flowBuilder and command line

[babag1]

two, hopefully quick and easy questions.

i just installed the appimage on ubuntu studio and it seems to be running. in the preferences, under binary locations, the flowBuilder field is red. i'm not sure what to put in here since i didn't compile but downloaded the appimage instead.

second, i'd like to run slomovideo from the command line for accuracy. while i appreciate the elegance and intuitiveness of the graphical interface, i'd like to try some very simple operations as i get started, things like, 'let's slow this video by exactly 4x, or 5x.' the website gives command line examples of how i might do this but, again, i don't know what the command should look like given my appimage installation.

and, needless to say, i've now thought up a third question. ffmpeg is installed on my system via snap. i don't know if that has anything to do with it but, no matter if i select video or images, it renders png files in a 'rendered' directory in my project directory. i'm guessing that might have to do with finding ffmpeg or flowBuilder?

and, lastly, there had to be another, the 'optional arguments' section shows the 'use quicktime' box as grayed out. if i want to render as prores, what exactly goes in to the field next to 'vcodec'? for ffmpeg i usually use something like '-c:v prores_ks -profile 3'.

thanks so much for any attention you can spare here and for what looks like a great piece of work!
babag