P: A way to create a custom crop overlay.

Hello,
I am a portrait photographer and I often take corporate photos, in this case, I have a large number of photos to crop while keeping a uniform appearance. I would like to have a custom template grid allowing me to crop easily a whole batch of photos

The nearest function possible in Lightroom-Classic is a 'Layout Image' overlay, but it is not real useful as it disappears when you choose the Crop Tool.

It is useful when Camera Tethering as you can position the camera view to place and size a 'face' view.

Correct.  If you've shot hundreds of school portraits and want to make all their heads the same size using the crop tool, lightroom currently does not have an easy overlay that allows for this.  An oval that could surround the face, or better yet, A.I. that detects their eyes and then applies a crop based on that so all faces come out same size.

Wondering this too!!! 

Yes!! I need this too for headsizing!  It would be nice to create a custom overlay in Photoshop, and then upload into Lightroom.  Or for lightroom to be able to have custom lines created at specific distances, and/or ovals.  How is this not an option?!

What I am looking for has nothing to do with the aspect ratio.  I want a better option to use as a cropping overlay.  Thirds, Grid, Diagnal, Center, Triangle, Golden Ratio, Golden Spiral, and Aspect Ratio are the only current options.  I am trying to just send in a suggestion to Adobe to add a better option for those who would like to create their own custom overlay.  

From a similar posting, but for 1:1, modify for your desired 5:7

So, in the screenshot below, I have selected the crop tool, I have not specified a crop ratio. And my default overlay shows up (Thirds)

Now, I can change the overlay, in the below, to Aspect Ratio

select just tour desired ratio

I think the OP wants to have a specific overlay shwon when cropping.  The grid lines shown.

@Tanya5E41  I can't quite picture what you are asking for. How would it know where to position it's self? If that is what you are asking for.

I am looking for a crop overlay, not custom aspect ratio.  I crop all my portaits at 5x7.  A custom overlay would adjust with your image as you crop in, the same way the grid or rule of thirds overlays do.