Cannot extend non-system bitlocker partition

The "Extend Volume" command is greyed out when trying to extend a Logical NTFS drive, despite there being unallocated free space to the right with nothing in the way.

Is this because of Bitlocker? I searched extensively but couldn't find anything saying that BitLocker stopped this happening.

The partition is encrypted using Bitlocker but I have tried:

• suspended bitlocker
• turning off bitlocker (decrypted the entire D drive)

and it still won't let me do "Extend Volume".

So I eventually solved it like this:

1. Open windows command prompt with administrator privileges
2. Type diskpart and press enter
3. list disk and then select disk 0 (or relevant number) to select the disk
4. list volume and then select volume 2 (or relevant number) to select the volume
5. Then simply extend and this extended the D drive to fill the available space to its right!

I think the reason Windows couldn't do it from the Disk Management GUI is that it's inside an "Extended partition" and so there wasn't space inside that to extend D, without also extending the extended partition around it (marked in dark green). And clearly it's not clever enough to do this for you (although it can from diskpart!)