UPDATE: It works now at my PC (14.0.1 - CC2019)

1. Stopped InDesign
2. Deleted all preferences of InDesign (<user>/library/Preferences/Adobe Indesign)
3. Restarted InDesign (everything is at default now)

Scaling does work now (proportionally) when pressing Cmd+Shift and moving corner of (group of) pictures.

Does not work here either after update to 14.0.1 ! Same with pressing SHIFT key and move an item horizontal, that also does not work anymore. And no, I'm not using Webroot or anything like that.
Workaround via Scale-tool ('S') as mentioned below is possible for proportional scaling (thanks!) but very annoying.
Why is this??

Write string
Create file PSUserConfig.txt with string "TransformProportionalScale 0" and add file to this directory

macOS: //Users/[UserName]/Library/Preferences/Adobe Photoshop CC 2019 Settings/

Hi I'm having the exact same problem since a few months running CC18 on Macbook running Mojave 10.14. Its infuriating!!
I am not running Webroot or anything either.
Can't find a fix for this.

For what it’s worth folks:

Been having a play this morning, and if you take it slow and be very deliberate about your intention to rescale something proportionally, Indesign does seem to acknowledge this - albeit temperamentally.

Use the Scale Tool rather than just the Selection Tool, hold down the shift key before clicking on a point and draw the point in as closely as you can on a 45 degree angle. Seem to work most of the time - even with grouped elements.

Not a fix by any stretch, but might get us all through (somewhat slower and frustrated) until this lot get their act together.

Hope it works for you.

I’m not running any anti-virus software of any kind and it’s still an issue. Come on Adobe, sort this out! It’s fundamental stuff!

I can see the posts of people saying it's automatically set now to scale proportionally, but that's not actually functioning. I cannot get anything to scale to proportion. This is an actual outrage. Why update if everything breaks????

Both me and my colleague are using CC version 14.0 but theirs has no issue, mine does?? what did I do to offend you? But seriously, this really sucks, please sort it out.

Same issue here with no antivirus software installed. I can't believe we are still waiting for this to be fixed!?!! We certainly pay enough for these programs.

I do not have Webroot or other antivirus software installed. This is a big problem. Even when the "constrain proportions for scaling" icon is selected and I hold down the shift key, it does not work. Please fix asap.

I am having same issue in Photoshop, do not have Webroot. Please fix, this is a mess.

you don't have to hold shift anymore to keep it proportionate.

When I am trying to scale a placed image using Shift+Option+Command on my Mac running OS Mojave, InDesign is only allowing me to scale the window, cropping the image as opposed to proportionately scaling the image as it has always done in the past. I've tried to quit Webroot SecureAnywhere app and restart InDesign and have renamed Library files as have been described and advised in other posts without success. All other posts I've seen with similar issues are only mentioning that the Shift key is not working properly (due to the change in the way that InDesign handles scaling in this latest version). My issue seems to be different.

If you have Webroot installed and are experiencing this problem on a Mac, click the Webroot icon in the header bar at the top of the screen. Click "Pause secure keyboard entry" from the dropdown menu and it should provide a quick fix to the problem. It worked for me, I hope this helps!

I have been a loyal user for many years. This is a big issue. That shortcut and functionality allowed the designer to be fast and efficient. This will slow me down... annoying!!!!!! stupid, just simply stupid. I wonder why this was dropped or if it's just something that was missed?

This is STILL not working. I do not have Webroot installed, your solution does not fix this problem. It works in Photoshop and Illustrator, but not InDesign. This is such a core functionality of InDesign, it's making it very difficult to use this software at all.

please help with this issue adobe ^^ this has been happening BOTH in the 2018 and 2019 versions and it's making using the program impossible!
the object won't hold it's proportions while rescaling

Proportional scaling now is enabled by default. No need to use the shift button.

Well, good to see it's a recent issue. For the record, I don't have any software of that sort installed. Running into this issue with Photoshop since 2019 update.

I don't have Webroot SecureAnywhere installed either.