wanna change size of vhdx from which windows was booted

So there is a problem, I have Server, Windows Server 2016 boots from vhdx( native boot or something, don't remember). So the problem is that at first installation I set really small size of vhdx, 40 Gb, don't know why, but I did, my bad. At first, it was enough for stable work, but now I have only 5 Gb free space and wanna expand vhdx disk to 100 Gb. So in this windows booted from vhdx, I open Hyper-V and press editing vhdx, I can choose the vhdx with Windows, and it looks like I can change the size of it, but I don't know what'll happen when I press proceed. I have some doubts about it. Could it be changed without any consequences? BTW vhdx is fixed, not dynamic. Problem is that there are a lot of users using server every day, I can't just risk to shutdown the server. Problem not critical yet, and Server will work normally for some time. For those who might say that this forum about Windows 10 - It doesn't matter, 'cause it's all the same +/- The same situation can exist with Windows 10.
Will be glad to hear some thoughts about the problem.

cereberus said:

I have changed sizes loads of times

Another non intrusive way is to create a new larger .vhdx file, mount both as drives and clone old .vhdx drive to new drive. Then extend partition in new drive.

I have changed sizes of other vhdx lots of times too, but all of them didn't runs system at the time
would it work while the system runs from that same vhdx? Let's say I have vhdx X and my windows running from that disk X, can I change size of vhdx X through windows that runs from vhdx X?

You can't resize a .vhdx while it is running. OR it isn't recommended.

see here:
How to Resize Virtual Hard Disks in Hyper-V 2016