If a recovery partition sits between C drive and unallocated space, Windows Disk Management cannot extend C drive. Moving the recovery partition can make the space usable.

Disk Management extends a volume only into adjacent unallocated space on its right side. A recovery partition between C drive and free space blocks the operation.
Use this workflow when the disk layout is C drive, Recovery partition, and then unallocated space. The goal is to move the Recovery partition to the right, so the unallocated space sits directly behind C drive.
Open Qiling Disk Master and check the system disk. Confirm that the Recovery partition is between C drive and the unallocated space. Create a system backup before moving any system-related partition.

Select the Recovery partition and choose Resize/Move. Drag the whole partition to the far right side of the unallocated space. Do not resize or delete the Recovery partition in this step.

Review the disk map. It should show C drive followed by unallocated space, then the Recovery partition. Click Proceed and allow the computer to restart if required.
After the move finishes, select C drive and choose Resize/Move. Drag the C drive border into the adjacent unallocated space until it reaches the size you want.

Click Proceed to extend C drive. After Windows starts, open an elevated Command Prompt and run reagentc /info to confirm the Windows Recovery Environment status.
Moving the Recovery partition is safer than deleting it when you still need Windows recovery tools. Back up first, move the blocking partition, extend C drive, and then verify WinRE.