I don't know about the app that you've mentioned but maybe try the lessons on this site, one section has minor piece training and the Knight is part of that.
Knight training/drills

Thanks. I went to Puzzles > Endgame > Minor Pieces > Knight, and was feeling rather hopeful. The only bummer is that it has me using a queen/king in an endgame 'against' a knight, rather than letting me play 'with' a knight. This is kind of close to what I wanted, but backwards. Oh well.
Here are a few other things that I've found so far.
https://www.danheisman.com/chess-exercises.html
https://www.amazon.com/Chess-Mazes-Kind-Puzzle-Everyone/dp/1888690232
https://www.chess.com/article/view/chess-micro-drills
Sorry about that, I haven't tried all of the lessons yet but seen that and thought it might be what you're looking for. I did try a Google search though and a lot of results came up, videos on YouTube is one example, I searched for the following....chess Knight training, try that and see if anything comes up that might be more help.
You could also make a suggestion in the feedback section of the forum, if it will help you and other players it might be worth considering.

Just imagine the knight is a unicorn. It's a horse, but it can fly. Compared to the other pieces, it's unpredictable and unique. I know that sounds silly, but it's what I actually do.

Thanks. I see Ben Finegold has a video...basically the same thing as the chess micro drill technique that is in one of the links above. All I have to do is place a knight and some other piece on the board, and then maneuver to it (without landing on spaces where I could be 'taken'). So simple and free. Pretty awesome how he flies around the board.
Is there a way to get a blank practice board on this site, where I can set this up and play against myself like he does?
https://www.youtube.com/watch?v=SrQlpY_eGYU
A couple of exercises from a video that helps just moving the knight around obstacles.
1.) move the knight from b1 to c1 avoiding a queen:
https://youtu.be/wMHr2xlnfkw?list=PLQKBpQZcRycrvUUxLdVmlfMChJS0S5Zw0&t=76
2.) Move the knight from a1 to b1 (and beyond) against a set of pawns:
https://youtu.be/wMHr2xlnfkw?list=PLQKBpQZcRycrvUUxLdVmlfMChJS0S5Zw0&t=306
Mikewrite: I setup #1 in a liChess study (and it looks like the same Finegold video) -- I added a king that moves back and forth for black's moves: https://lichess.org/study/eBIL0zp8

Appreciate the links. I just started watching Robert Ramirez yesterday. Good stuff.
Looks like I can set up a 'study' like you mention under Learn > Classroom.
Thanks to everyone for helping me figure all this out.

I mention this because I think I wasted a bit of time doing these types of exercises (and visualization also), when it was useless to do them out-of-context at my low level … a lot of the basic “skills” I was trying to improve upon came more naturally with thorough tactics training using thousands of simpler tactics problems (2-4 moves in depth).

I found an online drill workout for knight movements. this thread is old but maybe someone can found it useful.
https://chess.braimax.com/play/knight_vision
Some players seem to effortlessly navigate their knights around the board...while I usually have to sit and analyze how to get from point A to B. This especially sucks during endgame.
Anyone know of any resources for improving my ability to move the knights around better? The Magnus Training app has some drills where you have to maneuver your knight around the board and hit a number of spots within a period of time. That's pretty good. It's just that I have to wade through a whole bunch of other sequenced drills to get to these in the app. Just wondering if there are other knight maneuvering drills like this elsewhere?
Thanks, Mike