Split/merge channel options are greyed out in Files tab of browser when the files are on a Samba share. Copying to local drive makes the option active.
Please see ticket "Request #845123 Split/Merge not supported on network drives"
The stated reason for non-resolution is "We have seen this before in Studio One and the program is unstable on networks/network storage/clouds/NAS or remote systems"
Note that in Studio One+ saving, exporting, autosave, and mixdowns all work perfectly to the Samba network drive. So it seems peculiar that audio track split/merge is singled out for exclusion. I also routinely edit/render videos to the same network drive without issue.
-james