repartitioning a dual-boot SSD - which tool to use?

[StubbyTomatoes]

Hackingtosh working fine with dual booting OSX High Sierra (APFS) and Windows 10 on a 250GB SSD.

Now I need to shrink the OSX partition and grow the Win10 partition. I'd rather do it non-destructively. Any advice on what software to use?

 

[P1LGRIM]

Moved to Multi booting.

 

[vulgo]

Hackingtosh working fine with dual booting OSX High Sierra (APFS) and Windows 10 on a 250GB SSD.

Now I need to shrink the OSX partition and grow the Win10 partition. I'd rather do it non-destructively. Any advice on what software to use?

Resize APFS with diskutil. See

diskutil apfs resizecontainer

example:

diskutil apfs resizecontainer disk1s2 limits

and also

diskutil apfs listsnapshots

example:

diskutil apfs listsnapshots disk2s1

Snapshot for disk2s1 (1 found)
|
+-- Name: com.apple.TimeMachine.2018-04-25-064638
XID: 1160556
NOTE: This snapshot sets the minimal allowed size of APFS Container disk2

the missing pieces of the puzzle:

tmutil listlocalsnapshots /Volumes/Macintosh\ HD

and

tmutil deletelocalsnapshots <snapshot_date>

APFS works best when you give it the whole disk...

 

[Going Bald]

If Win10 is installed on the second half of the drive your best bet is to get another drive, move Win10 to the new drive and extend your Mac OS APFS partition to include the entire drive.
Either that, or shrink the Mac OS partition, delete the Win10 partition(after backing it up), create a new partition to include the freed-up part of the drive and restore or re-install Win10.