The Extended Volume feature in Windows Disk Management can increase partition size. Here's what to do when it's greyed out and you can't use it.

If Mark Partition as Active, Change Drive Letter, Format, Extend, Shrink, Delete Volume options are greyed out in Disk Management, see this post.

If the "Extend Volume" option in Windows Disk Management is grayed out, you might want to try AOMEI Partition Assistant. It is easy to fix the problem, and no data will be lost.

If the Delete Volume option is greyed out for USB Flash drive on Windows 11/10, use the methods in this post to delete the partition.